Further improvements

Hi,

I finally managed to implement those two changes we agreed upon:

* the route-like syntax now can also take non top-level objects like "admin/task#update"
* the custom matchers are now under `lib/spec_helpers` and can be used in rspec by requiring  `websocket_rails/spec_helpers` in the `spec_helper`or in the single spec file.

I promoted `Event.encoded_name` to be a public method because I needed it in the matchers to output a meaningful failure message.
I also add the development dependency to a small gem I made which allows for testing of the failure messages outputted by custom matchers.

When this pull request is merged I can write a Wiki page to explain how to use the custom matchers to test the events file and the controller functionality.