Support duplicate query params when interacting with the Echo Nest API

In order to retrieve track data (e.g. preview_urls, audio summary info) it's necessary to include multiple `bucket` params. This pull replaces the base class' query param building with standard HTTParty usage. HTTParty already handles duplicate params properly, plus it's just less code in echonest-ruby-api.

Note the use overridden query_normalizer: `HTTParty::Request::NON_RAILS_QUERY_STRING_NORMALIZER`. We need to use this normalizer, otherwise duplicate query params are formatting like `?foo[]=bar&foo[]=baz`, which Echo Nest doesn't support.