Notebooks should refer to resources in this repository

[jayvdb]

In an offline environment, the tests fail because they load the notebooks, and the notebooks refer to files in pyexcel-chart repo

notebook/life_expectancy.ipynb:    "sheet = p.get_sheet(url='https://github.com/pyexcel/pyexcel-chart/raw/master/docs/source/API_SP.DYN.LE00.IN_DS2_en_csv_v2.csv')\n",

I'll try some magic to pull these files into the build environment and use local files instead.

[jayvdb]

Magic done, tests still failing https://build.opensuse.org/package/show/home:jayvdb:pyexcel/python-pyexcel-pygal