Added an Esperanto (eo) translation.

During testing (on OS X), I noticed that there was at least three instances of English that didn't get translated into Esperanto.

1. 'Help' in the menu bar
2. 'Project' in the project/filetree tab
3. 'Toggle bookmark' tooltip in the tool bar 

I also tested those in most of the other available languages to see if I potentially screwed something up, and they weren't receiving translations either. FYI