Update some markdown files

Author: DanielGoldfarb

CONTRIBUTING.md

@@ -1,10 +1,9 @@
 - Contributing can as simple as **asking questions**, participating in discussions, suggesting enhancements, etc.  **All of these are valuable!**  There are many ways to contribute.
 
-- All of the usual/typical open source contribution guidelines apply (see for example, **[Matplotlib Contributing](https://matplotlib.org/3.1.1/devel/contributing.html)** and **[Open Source Guide to Contributing](https://opensource.guide/how-to-contribute/)**)
-so here, on this page, we will mention just a few items for which we may be particular in **mplfinance**.
+- All of the usual/typical open source contribution guidelines apply (see for example, **[Matplotlib Contributing](https://matplotlib.org/3.1.1/devel/contributing.html)** and **[Open Source Guide to Contributing](https://opensource.guide/how-to-contribute/)**).  Therefore, here, on this page, we will mention just a few items that we may be particular about in **mplfinance**.
 
 
 - Coding:
   - If you write code, please don't use tabs; rather use spaces.
-  - If you add a significant feature, that is a feature for which explaining its usage takes more than just a few sentences, please also create a "tutorial notebook" for that feature.  **[For examples of tutorial notebooks, please see the jupyter notebooks in the examples folder.](https://github.com/matplotlib/mplfinance/tree/master/examples)**
+  - If you add a significant feature --that is, a feature for which explaining its usage takes more than just a few sentences-- please also create a "tutorial notebook" for that feature.  **[For examples of tutorial notebooks, please see the jupyter notebooks in the examples folder.](https://github.com/matplotlib/mplfinance/tree/master/examples)**
   - If you add a significant feature, please also create a regression test file **[in the tests folder](https://github.com/matplotlib/mplfinance/tree/master/tests)**, similar to the other regression tests that are there.  *Often, the simplest way to do this is to take a few of the examples from the feature's "tutorial notebook"* (see previous point).

README.md

@@ -21,8 +21,9 @@
   - **[The New API](https://github.com/matplotlib/mplfinance#newapi)**
   - **[Tutorials](https://github.com/matplotlib/mplfinance#tutorials)**
     - **[Basic Usage](https://github.com/matplotlib/mplfinance#usage)**
-    - **[Customizing the Appearance of Plots](https://github.com/matplotlib/mplfinance/blob/master/markdown/customization_and_styles.md)**
+    - **[Customizing the Appearance of Plots](https://github.com/matplotlib/mplfinance/blob/master/markdown/customization_and_styles.md)** (**New** features June 2020)
     - **[Adding Your Own Technical Studies to Plots](https://github.com/matplotlib/mplfinance/blob/master/examples/addplot.ipynb)**
+    - **[Subplots: Multiple Plots on a Single Figure](https://github.com/matplotlib/mplfinance/blob/master/markdown/subplots.md)** (**New** June 2020)
     - **[Price-Movement Plots (Renko, P&F, etc)](https://github.com/matplotlib/mplfinance/blob/master/examples/price-movement_plots.ipynb)**
     - **[Trends, Support, Resistance, and Trading Lines](https://github.com/matplotlib/mplfinance/blob/master/examples/using_lines.ipynb)**
     - **[Saving the Plot to a File](https://github.com/matplotlib/mplfinance/blob/master/examples/savefig.ipynb)**

markdown/customization_and_styles.md

@@ -4,15 +4,15 @@
 
 ---
 
-### Use ` mplfinance styles ` for _general_ customizations applied to many plots,<br>for example:
+### Use [` mplfinance styles `](https://github.com/matplotlib/mplfinance/blob/master/examples/styles.ipynb) for _general_ customizations applied to many plots,<br>for example:
 - colors  (candle colors, moving average colors, background, grid and figure colors)
 - grid style
 - y-axis on the right or left
 - matplotlib defaults
 
 ---
 
-### Use key word arguments for specific/individual plot customizations,<br>for example:
+### Use key word arguments for [specific/individual plot customizations](https://github.com/matplotlib/mplfinance/blob/master/examples/plot_customizations.ipynb),<br>for example:
 - figure size and aspect ratio
 - display of non-trading periods (weekends, holidays, after hours trading)
 - figure title
@@ -21,10 +21,10 @@
 - x-axis labels rotation
 - line color for line plot
 - tight_layout
-- candle and line widths
+- fill_between
 
 ---
 
 ### Other features related to customization:
-- subplots
-- fill_between
+- [**subplots**](https://github.com/matplotlib/mplfinance/blob/master/markdown/subplots.md)
+- [**candle and line widths**](https://github.com/DanielGoldfarb/mplfinance/blob/master/examples/widths.ipynb)

markdown/subplots.md

@@ -28,7 +28,7 @@
 ---
 
 ### The Matplotlib Method
-* **NOTE: This method is _not yet implemented_.  It is presently expected to be available by the end of June 2020.**
+* **NOTE: This method is _not yet implemented_.  It is presently expected to be available by the end of July 2020.**
 * The `matplotlib` method requires the user to call various matplotlib methods, external to `mplfinance`, in order to create a Figure and Axes (**SubPlots**) that the user then passes into `mpf.plot()`.
   - **The user is responsible** to configure the size and location of the Axes objects within the Figure.
   - **The user is responsible** to display the Figure (as mplfinance will not `show()` the Figure).