Merge pull request #23 from zendesk/grosser/cleanup

cleanup rakefile
remove shoulda
Merge pull request #24 from zendesk/grosser/shoulda

remove shoulda
make asserts easier to debug when they fails
reset storage engine properly
unify cleanup and always use it
Merge pull request #25 from zendesk/grosser/tests

cleanup tests a bit
Rename Gemfiles
Test against Rails 4.1 & 4.2
Connect with a symbol, avoid the warning
Make assertions on table more explicit
Replace alias_method_chain with prepend on Migration directly