Added a test for files moved to another directory.

See #6
Allowing urlPrefix ovverride:

* Actually attaching buildOverridesDefinition tot he processed stuff so it's conctest can actually have effect
* assignPrefix should now not override urlPrefix if we catually have one assigned!
* Fixed broken non-failing Tests
* Enhanced Readme
* Adding missing tests
Merge pull request #7 from unlucio/allowing-arbitrary-urlPrefix

Fix for allowing urlPrefix override
Merge branch 'master' of https://github.com/jussi-kalliokoski/gulp-spa

Conflicts:
	lib/builtins/html/findBuilds.js
	lib/utils/assignPrefix.js