this way if the expectation fails, it won't pollute other specs.
as opposed to shelling out to `rake test`, which was slower. assumes that tests are located in the "test" directory
Rspec 3.0 introduces separate _helper files for full tests and tests that don't require the full rails app to be loaded. Because of this and because the point of zeus is to pre-load your app, default to loading the full rails_helper for zeus. You can override this behavior with the env var RAILS_TEST_HELPER. Fixes #474
The default make command tries to make the darwin version of the gem which will not work on linux due to the absence of XCode. This adds back a make linux command to allow building just the linux binaries.