added model for post history (#18)
removed controller specific js from layout

we merge all js files together anyway, so it was a duplicate
post validations
renamed member_role to role
re-added spork-testunit, it should solve issues revolving staring drb server
added member_role model again for has_many :through

roles and members has a many-to-many assoc
has_many :through so it can be observable for adding and
removing roles
spork now will reload models too
added observer for creating post history
controller and views for adding and editing arbitrary posts, closes #18
added post history.

now we keep track of how roles changed for a member