using 'public' urls for rebar dependencies

Hello :)

I have a use case, where an open source project (having a dependency on worker_pool), is built by a jenkins box without ssh credentials for github. Using **git@** for dependencies in worker_pool would not work, so I've updated the urls to use **https://** instead.

Also, expecting the 2.0.0 version of lager on master [does not work anymore](https://github.com/basho/lager/blob/master/src/lager.app.src#L6), so I've pointed it to the [right release](https://github.com/basho/lager/releases/tag/2.0.0).

Cheers!