Install Appraisals

Testing versus activerecord 4.0 & 4.1
Added Appraisal rake task
Doesn't work anymore with ActiveRecord 4.1.0

From what I could tell from the rails source it seems like this is no
longer supported.

https://github.com/rails/rails/blob/v4.1.0/activerecord/lib/active_record/connection_adapters/connection_specification.rb#L123-L158
Merge pull request #31 from mcls/master

Test against ActiveRecord 4.0.4 and 4.1.0