Fix supported Ruby version in README
Fix supported Ruby version in README

* Claim is not actually true: various Ruby 1.9/2.x syntax usages in codebase
* 1.8.7 is no longer supported
jajuki13/representable,tastyworks/representable,simonoff/representable,tastyworks/representable,apotonick/representable,rusikf/representable,irfanah/representable