Enable transpiling for ember-runtime.
Refactor EnumerableTests suite to ES6.
Cleanup ES6 imports for ember-runtime.
Refactor ember-runtime/tests/suites/suite.

Previously, we relied on side-affects of the minispade `require` to
ensure that all of the tests and modules were added to the same global
object.  In ES6 land this won't work as each of the imports returns the
original class/function.