Update CSP addon.

Now uses `Content-Security-Policy-Report-Only` by default.
Merge pull request #2190 from rwjblue/make-CSP-report-only-by-default

Update CSP addon.
Update broccoli-sane-watcher version.
Allow addons to customize es6 module prefix

Addons can now customize the module prefix they are compiled under:

```js
// index.js

module.exports = {
  name: 'some-addon',
  modulePrefix: 'other-addon'
}
```

Normally addons would use `name` to compile under. If `modulePrefix` is
declared that is used instead.

Use Case!!

During the ember-validations rewrite I've realized that I'd like to have
another library: ember-validations-addons or something to that effect.
It will contain additional validators that don't need to be part of the
original library. (like the URI validator) But I still need to lookup
validators in the `ember-validations` namespace rather than attempting
to manage additional namespaces. This would allow others to also write
their own addons in the same namespace.
Merge pull request #2189 from bcardarella/bc-custom-addon-module-prefixes

Allow addons to customize es6 module prefix
Merge pull request #2191 from rwjblue/update-sane-watcher

Update broccoli-sane-watcher version.
Ensure all addon hooks are executed in addon test harness.

Previously, when using the `tests/dummy/` app in an addon project, the
only hooks that were called were build related (because we only added
the addon project to the `addons` list in the `Brocfile.js`).

Now, we always add the addon project. This allows testing commands,
blueprints, middleware hooks, etc.
Merge pull request #2195 from rwjblue/addon-hooks-in-addon-project-dummy

Ensure all addon hooks are executed in addon test harness.
Add description to addon command.

Without this, it inherits the description from `ember new`.
Merge pull request #2196 from rwjblue/addon-description

Add description to addon command.
Bump version.