ember-runtime single var assignment per declaration

I am working through a code style cleanup effort using
[jscs](https://github.com/mdevils/node-jscs) rules.

You can see the script and rules in:
https://github.com/rwjblue/ember.js/compare/code-style-rules
Merge pull request #5356 from rwjblue/single-line-var-runtime

ember-runtime single var assignment per declaration