Fixed basic auth during the initiliazing of cypher session, closes #57

* Fixed auth params not getting passed properly to HTTParty during some POST requests which contain data
* Accomodating multiple sessions and a bit of refactoring
* Passing the Neo4jServerEndpoint around CypherTransaction, Resource in order to wrap HTTParty
* Added tests for Neo4jServerEndpoint and cleaned up the tests for CypherSession
Allow all HTTParty's options for Neo4j Sessions, #51

See https://github.com/jnunemaker/httparty/blob/master/lib/httparty.rb