fix syntax hightlighting in docs

When using comments in a pycon session, comments must be prefixed with standard
console prompt (>>>) for pygments syntax highlighting to work.
refactor the blob example
Merge remote-tracking branch 'esc/docs/fix_syntax_highlight'
Coding style

Including:

- Lines longer than 79 chars
- Spaces at the end of line
- Wrong indentation
- Comma not followed by an space
- C++ style comments: //
Update copyright
Now we have a Repository class written in Python
_pygit2.init_repository doesn't use keyword args