Update testem config for sauce labs runs.
Update testem config for sauce labs runs.

* Adds Microsoft Edge
* Updates Chrome to use `latest` and `latest-1` (was using 39 and 38)
* Updates Firefox to use `latest` and `latest-1` (was using 34 and 33)
* Updates Safari to use 9 and 8 (was 8 and 7)
* Wraps `<url>` in quotes to avoid issues with quoting discovered in Ember.

tildeio/glimmer,tildeio/glimmer,lbdm44/glimmer-vm,chadhietala/glimmer,chadhietala/glimmer,chadhietala/glimmer,glimmerjs/glimmer-vm,lbdm44/glimmer-vm,lbdm44/glimmer-vm,glimmerjs/glimmer-vm,glimmerjs/glimmer-vm,tildeio/glimmer,chadhietala/glimmer