Allow a different Blueprint directory to be specified for Init and New commands
Remove specifying rootURL from ENV

Specifying a rootURL should be optional and not based on the ENV rootURL, which should only be used to namespace assets in the `base href` tag. The previous functionality resulted in a bug where you would get a double url parameter if you serve your app from `/foo/index.html` and also specified a rootURL `/foo`, giving you `/foo/foo`. The router rootURL should be an opt-in configuration based on how a user decides to deploy their app.

https://github.com/stefanpenner/ember-cli/issues/417
Commands Init & New
1. change available option 'blueprint-path' to 'blueprint'
2. add acceptance test for 'blueprint' option
[changelog] Document blueprint argument for New and Init
Merge pull request #462 from monocle/refactor

Allow a different Blueprint directory to be specified for Init and New commands
Merge pull request #464 from denisnazarov/patch-1

Remove specifying rootURL from ENV
Use new `tmp/output` location for Testem.

This allows using the command line version of `testem` in addition to
running in CI mode (the current behavior).