Use quoted action name.

As of Ember 1.4.0-beta.5 using the unquoted version is deprecated. Using
a quoted string is totally backwards compatible so this is a
non-breaking change.

Ember 1.5.0 will use unquoted action names and performed property
lookup, allowing for dynamic actions. We will have to decide
how to handle these dynamic action names at some point
(likely after 1.5.0 ships).
Merge pull request #56 from rjackson/quote-action-name

Use quoted action name.