Removed problematic methods; rails3 seems to work

Rails has changed the way callbacks work; now the public-facing
api is much better, and can be used outside ActiveRecord, rails, etc.
Unfortunately, it looks like it might be difficult to make the way
attachment_fu hooks into rails 2.X work in rails 3. The documentation
for set_callback alludes to something that might work (specifically,
supporting passing in a non-self argument to the callback), but
the examples it uses in this regard don't seem to be accurate anymore.

Oh well, this *seems* to work for now.
Add gemspec
rails/ init files
Merge branch 'master' into rails3
Actually try and work.
rails/init.rb not loaded in gems? WTF is that.
specifically require backends
gem-ify works finally
proper callbacks in children.
Fix bug
Fix processor requirements
processor inclusion
Yank debugging
returning => tap
rails3
Works, now working deprecation warnings
bump version for RAILS_ROOT removals
RAILS_ENV => Rails.env for 3.1
Update gemspec for Rails.root change
added yousty processor