saucelabs browser specification should probably not be merged

[trentgrover-wf]

If you specify specific browser configurations for testing via sauce labs in the wGulp gulpfile.js, these entries are merged with the existing default entries provided by wGulp. This may result in unintentionally running sauce labs tests with unnecessary browser configurations.

If a browser config is specified locally, it should probably just completely override the wGulp defaults (instead of merge with them).