Run test with Ruby 2.1 on Travis CI
Run test with latest ember-source
Use `debug: true` option instead of `ENV['THOR_DEBUG']`

In rails4, `run_generator` seems to be run with clean env.
thor couldn't raise error against expectation without this debug option .

This patch fixes some failing tests using `assert_raise`.
Merge pull request #365 from tricknotes/fix-failing-tests-in-rails4

Fix failing tests in rails4