Adapt ember-moment to htmlbars new helpers signature

In htmlbars helper methods have a different signature. This PR defines one function or another based on the presence of `Ember.HTMLBars`.

Also fixes some annoying deprecation warnings in apps using htmlbars.
`helper` will make a bound helper for you. Using `makeBoundHelper` in the helpers files is not needed, and I am surprised it works ;-)

I suggest dropping the `makeBoundHelper` code.