feat(e2e): Added E2E testing

Tests are defined in `*.scenario.*` files.
Data fixtures defined with `ngMockE2E:$httpBackend.when()` calls are defined in `*.fixture.*` files.
Data fixtures are only included in `build`, for development, not `compile`.
The Karma ng-scenario adapter is statically included as a temporary fix until it can be included as a sibling dependency:
https://github.com/karma-runner/grunt-karma/issues/13