Removed 1.9.3 compatibility mention
**Ruby**
-Oj is compatible with Ruby 1.9.3, 2.0.0, 2.1, 2.2, 2.3, 2.4 and RBX.
+Oj is compatible with Ruby 2.0.0, 2.1, 2.2, 2.3, 2.4 and RBX.
Support for JRuby has been removed as JRuby no longer supports C extensions and
there are bugs in the older versions that are not being fixed.
