Improve docker test-env builds

 * Let the container run in the non-interactive mode and uses slightly less disk space.
 * Update/add .gitignore and .dockerignore to exclude a local virutalenv if exists.

.dockerignore

@@ -0,0 +1,3 @@
+venv*
+virtualenv*
+*.log

.gitignore

@@ -65,3 +65,8 @@ target/
 # Project
 tags
 ci/aioodbc
+sqlite.db
+
+# virtual envs
+venv*/
+virtualenv*/

ci/Dockerfile

@@ -1,4 +1,10 @@
-FROM python:3.5.2-slim
+FROM python:3.6.1-slim
+
+# configure apt to install minimal dependencies in non-interactive mode.
+ENV DEBIAN_FRONTEND noninteractive
+RUN echo 'APT::Install-Recommends "false";' >> /etc/apt/apt.conf; \
+    echo 'APT::Install-Suggests "false";' >> /etc/apt/apt.conf
+
 RUN apt-get update && apt-get install -y \
     unixODBC wget g++ unixodbc-dev odbc-postgresql libmyodbc libsqlite-dev libtool build-essential && \
     odbcinst -i -d -f /usr/share/libmyodbc/odbcinst.ini && \
@@ -10,6 +16,7 @@ RUN pip install -e /aioodbc/ && \
     pip install -U pip setuptools && \
     pip install -r /aioodbc/requirements-dev.txt
 
+# with --squash option in docker build, this will reduce the final image size a bit.
 RUN rm -rf /aioodbc && \
     rm libsqliteodbc_0.9992-0.1_amd64.deb && \
     apt-get purge -y g++ && \

ci/Makefile

@@ -1,2 +1,2 @@
 build:
-	docker build --rm -t jettify/aioodbc-test -f Dockerfile $(pwd)../
+	docker build --rm --squash -t jettify/aioodbc-test -f Dockerfile $(pwd)../