Removes deprecated methods in light of version 2.0
Code adjustments, mainly thanks to rubocop.
Unit tests adjustments
README, CHANGELOG and UPGRADING updates.
Releasing version 2.0.0
Delegates Point#sash_id to Score
README update
Mock in unit test
Rubinius requires sqlite3 in it's platform
Revert "Rubinius requires sqlite3 in it's platform"

This reverts commit a38230c4823d5d8fc5e8e4abdb96ca90eb641819.
Specific version of sqlite.

https://github.com/travis-ci/travis-ci/issues/2006#issuecomment-36275141
Mongoid tests corrections