Skipping spring for internal app generation

EngineCart was halting in spring-1.1.3/lib/spring/client/run.rb:54 as
Spring was attempting to start some semblance of a server.

Closes #15
http://stackoverflow.com/questions/23165506/rails-spring-breaking-generators
Merge pull request #16 from jeremyf/adding-skip-spring-option

Skipping spring for internal app generation