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
Include decorators when folding
Refactor folding.vim
Add folding for docstrings
Modify foldtext for docstring folding
Merge pull request #207 from alvinfrancis/develop

Modify folding
Update changelog
Update version
Merge branch 'release/0.6.16'
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