Moving service-specific calls to the service itself.

This includes:

* removing calls from client and moving them to service_client;
* using faraday as the http client so we can log requests in a simpler way;
* removing jeweler - uses bundler for gem management;
* changing default ruby to jruby;
* leaving test-unit for rspec so we can run a single example;
* migrating oauth code from hp-api here;
* migrating utility methods from hp-api here as well;