Now config can be also specified as an options to jekyll
Set proper jekyll, and rack versions allowed.
Updated .gitignore to follter .ruby-version, and .ruby-gemset files
Fixed 'auto' option for Jekyll > 2.0

Jekyll now uses a newer version of the Listen gem. The new gem doesn’t
support the old Listen syntax, and therefore the event never fires.
This fixes that by adding a “starting” the listener.