Add support for assertions in fixtures

By adding an `assertions` module, you can test the result of mop
on a file system level.
Exporting a shouldTestInBrowser property controls the execution of the 
fixtures in phantomjs.
Add bundling test for Montage
Add a test to assert the build directory
Fix JSHint warnings
Clear out shouldTestInBrowser
Add a quiet argument to clear out the noise.
Refactor knowledge of fixture paths
Merge pull request #3 from francoisfrisch/add-montage-specs

Add montage specs