Drop support for ruby ree, 1.9.2

End of life for 1.8.7 and 1.9.2 was July 31, 2014. This drops support for those versions. The major version will be bumped to reflect this. This is slated for a 2.0 release.
:+1: learned something new. Fixed in d80a65e9aaf35752505cf7043bc4274b1897d548