Offtopic, but should "fx_desktop_v1" be extracted out somewhere?

```
$ grep -ir "fx_desktop_v1" * | grep -v "dist"
app/scripts/lib/constants.js:    FX_DESKTOP_CONTEXT: 'fx_desktop_v1'
app/tests/spec/lib/router.js:        windowMock.location.search = '?context=fx_desktop_v1';
app/tests/spec/lib/router.js:        assert.equal(navigateUrl, '/forgot?context=fx_desktop_v1');
```

It looks like we have a constant for it already, but are using hardcoded values in ~2 places.
The opposite search `$ grep -ir "FX_DESKTOP_CONTEXT" * | grep -v "dist"` shows that we're also using the constant value in ~2 places as well.
```
app/scripts/lib/constants.js:    FX_DESKTOP_CONTEXT: 'fx_desktop_v1'
app/scripts/main.js:    if (context === Constants.FX_DESKTOP_CONTEXT) {
app/scripts/views/sign_in.js:                if (Session.get('context') !== Constants.FX_DESKTOP_CONTEXT) {
```

![Confused](http://www.unrealfacts.com/wp-content/uploads/2013/09/wtf.jpg)