Test against all Ember channels.

This updates to the latest `ember-dev` (56b02fa) which allows testing
against each Ember channel using the `emberchannel` URL param, and
updates the tests run by CI to run against all three channels.
Merge pull request #1498 from rjackson/test_against_multiple_versions

Test against all Ember channels.
[BUGFIX beta] Prevent error in failed reload().

Resolves #1511.
Merge pull request #1512 from rjackson/add_notFound_to_loaded_saved

[BUGFIX beta] Prevent error in failed reload().
Latest ember-dev uses local packages.

Builds are only published if all files are found, but the latest
`ember-dev` requires that `yuidocjs` be installed locally (in
`node_modules/`). Since `/docs/build/data.json` (the `yuidoc`
output file) was not found, the builds were not being published.
Merge pull request #1510 from rjackson/use_local_packages

Latest ember-dev uses local packages.