Set commentstring in pymode_options.

This setting is used in vanilla vim for adding fold markers, but also by
vim-commentary for using the appropriate comment marker for specific
filetypes.
Update documentation regarding commentstring.
fix Chinese runtime error

fix Chinese runtime error
Merge pull request #207 from alvinfrancis/develop

Modify folding
Update changelog
Update version
Merge branch 'release/0.6.16' into develop
Fix typo in option filtering

This also fixes an error where pymode_lint_ignore was not interpreted
correctly anymore.
Update pylama
Update autopep8
Merge pull request #214 from winged/develop

Fix typo in option filtering, causing possible syntax error
Merge branch 'develop' of github.com:klen/python-mode into develop
Merge pull request #203 from loyalpartner/develop

fix Chinese runtime error
Merge pull request #198 from dkasak/commentstring

Set commentstring in pymode_options.
Merge branch 'develop' of github.com:klen/python-mode into develop
Added AUTHORS file.
Update version.
Merge branch 'release/0.6.17' into develop
Refactoring code checking
Merge branch 'feature/rope' into develop