remove Object#tap, String#bytesize, and String#bytes extensions

these methods are all defined in ruby 2.0 which is the minimum ruby
version required by the oauth gem

Author: Charlie Somerville

lib/oauth/core_ext.rb

@@ -1,33 +1,3 @@
-# these are to backport methods from 1.8.7/1.9.1 to 1.8.6
-
-class Object
-
-  unless method_defined?(:tap)
-    def tap
-      yield self
-      self
-    end
-  end
-
-end
-
-class String
-
-  unless method_defined?(:bytesize)
-    def bytesize
-      self.size
-    end
-  end
-
-  unless method_defined?(:bytes)
-    def bytes
-      require 'enumerator'
-      Enumerable::Enumerator.new(self, :each_byte)
-    end
-  end
-
-end
-
 # TODO: Work around URI.escape obsolete method
 #
 # 21/May/2016 - We are silencing a warning introduced in 2009