Contribution prototype and stylistic adjustments

1. Adjusted line length to 99 chars, added spaces around commas, and operators, and removed a couple of end-of-line semi-colons.

2. Added requirements file. How about putting all documentation in a doc/ folder?

3. Added a method to retrieve the section titles, analogous to the get_section_ids in the connection class.

4. Put together a quick prototype of a package inspired in KF4’s Contribution tool in a folder called contrib_count. It uses matplotlib and numpy to build a quick graph. Google Charts might be better, but I'll need to study how to use it.