Add Code Climate badge to README

I also moved both the build status badge and the Code Climate badge to the top as I've seen a lot of other projects do.
Merge pull request #446 from noahd1/master

Add Code Climate badge to README
This gets Mongo and DataMapper specs running
but newer versions of AR, and incidentally Sinatra specs still fail.
Use database_cleaner ~> 1.2.0 for tests
use kaminari.gemspec database_cleaner in sub gemfiles
Use truncation for DataMapper
lock mongoid_30 at ~> 3.0.0
test against mongoid ~> 3.1.0 with rails ~> 4.0.0
allow some failures :trollface:
allow failures on travis for sinatra_13 and sinatra_14

based on a patch by @wbyoung #451