Add initial chart generator python file.

Followings are steps to install pygan and dependent libraries in Ubuntu:

$ wget http://peak.telecommunity.com/dist/ez_setup.py
$ sudo python sz_setup.py
$ sudo easy_install pip
$ sudo apt-get install python-dev
$ sudo apt-get install libxml2-dev libxslt-dev
$ sudo pip install pygal
$ sudo pip install CairoSVG tinycss cssselect # for PNG output
Append XY Chart sample code
Support generating chart automatically by using python library.

It depends on two famous python library:

   - pandas  - data analysis library (http://pandas.pydata.org/)
   - pygal   - chart svg chart creator (http://pygal.org)
Merge branch 'feature/generate_chart' into feature/top-risk-list
Collecting all 'churn-complexity.csv' file for all repos in a project and Generate chart as result.