switched imagesloaded from bower to npm dependency via browserify

[trabus]

Pulls in imagesloaded via browserify in an instance-initializer, and sets up dependencies in default blueprint.

[trabus]

I'm uncertain why these two unit tests are failing in only ember 2.8, from what I can see, according to this issue (emberjs/ember.js#12457) it should be failing in all of the ember-try scenarios because stubbing _super isn't technically supported.

[trabus]

I simply removed the _super check in the tests, since it's unreliable. We can still have a valid test to see if masonry is destroyed or not when the attributes change, and if the value is changing, obviously _super is being called.

[kellyselden]

I think if you split this PR into an update ember-cli PR and then start the tweaks, it would have better chance at being merged.