Use custom Main module
Use -Werror on travis only
Require hspec >= 1.12.1
Rename test/Spec.hs test/Main.hs
Update README
Use test/Spec.hs instead of test/Main.hs for now

(see https://github.com/hspec/hspec/pull/198#issuecomment-59725495)
Require hspec-2.*
Test private stuff