Leader on "jk" experimental feature, ido and coffeescript improvements and fixes

New experimental feature

• Leader can be triggered by pressing "jk" quickly in insert state, helm buffers and ido buffers. See documentation in readme.

Improvements and fixes

• New very cool functions available in ido minibuffer to open a buffer in a new window or frame as well as to browse the ido history, see documentation in readme (thanks to ralesi).
• < and > now correctly indent coffeescript code (thanks to danielwuz).