Merge pull request #44 from jordoh/handle_nil_prefix

Update starts/ends_with? to handle nil prefix

Author: dennisreimann

lib/openid/extras.rb

@@ -1,10 +1,12 @@
 class String
   def starts_with?(other)
+    other = other.to_s
     head = self[0, other.length]
     head == other
   end
 
   def ends_with?(other)
+    other = other.to_s
     tail = self[-1 * other.length, other.length]
     tail == other
   end