Update README.md

Author: Sunny Raj Rathod

README.md

@@ -9,7 +9,7 @@
 
 ## Prerequisites
 
-* Ruby 2.2.5 or higher
+* Ruby 2.1.0 or higher
 * RubyGem 1.3.7 or higher (to build the gem)
 * RDoc 1.0 or higher (to build documentation)
 * Rake 0.8.7 or higher (to use the rake tasks)