Indicate that the build was successful after a build error.

Prior to this change if a build errored it was not possible to know from
the console if that issue has been corrected. This forced us to stop &&
restart the server to get feedback (even though it had likely already
been fixed).

This change adds a "Build successful." message when the build had
previously errored (the stack was already printed to the screen), and is
now built properly.

@danmcclain / @rjackson
Instructions for using master
Merge pull request #412 from rjackson/show-rebuild-successful

Indicate that the build was successful after a build error.
Add test coverage for watcher rebuild message.
Create own tree for tests files and avoid testing files on ENV=production [fixes #409].
Merge pull request #424 from abuiles/test-files

Create own tree for tests files and avoid testing files on ENV=productio...
Add `ember test`.
Merge pull request #388 from abuiles/ember-test

`ember test` with Testem.
Detailed instructions on how to work with master
Add link to `npm-link` docs.
Merge pull request #425 from rjackson/add-npm-link-link

Add link to `npm-link` section of README.
Fix typo
Merge pull request #428 from HeroicEric/typo

Fix typo in package.json
Description on how to use the tests
Merge pull request #422 from rjackson/test-watcher-build-change

Add test coverage for watcher rebuild message.
update version to be clear when using master
Reformatted testing section, added "Development Hints" heading
Fix link texts
Fix mocha link href
Remove broccoli-env dependency