docstrings enhancement

This pull request covers these issues (enhancements):

 - https://github.com/srusskih/SublimeJEDI/issues/108
 - https://github.com/srusskih/SublimeJEDI/issues/133

I edited also the main readme file to inform about new commands availability, but didn't edit keymap file. So user would need to assign these 2 new commands by himself to be able to see them working.

Hope it's OK.