fix conflicting String#b implementation in ruby 2.x

.travis.yml

@@ -5,8 +5,7 @@ rvm:
   - 1.8.7
   - 1.9.2
   - 1.9.3
-  - rbx
-  - rbx-19mode
+  - rbx-2
   - jruby
   - jruby-19mode
 

lib/radix/operator.rb

@@ -48,13 +48,26 @@ class ::String
   #   The desired base.
   #
   # @return [Radix::Integer, Radix::Float]
-  def b(base)
+  def b_with_radix(base = nil)
+    # assume this is the ruby String#b being called if base is nil
+    return b_without_radix if base.nil? && respond_to?(:b_without_radix)
+
     if index('.')
       Radix::Float.new(self, base)
     else
       Radix::Integer.new(self, base)
     end
   end
+
+  # String#b in Radix conflicts with String#b in ruby 2.x
+  # to get around this without breaking the Radix API
+  # we can set up a method chain
+  if "".respond_to?(:b)
+    alias_method :b_without_radix, :b
+    alias_method :b, :b_with_radix
+  else
+    alias :b :b_with_radix
+  end
 end
 
 ##