Add NoExperimentError to replace NameError on missing experiment

lib/vanity/experiment/base.rb

@@ -211,4 +211,8 @@ def connection
 
     end
   end
+
+  class NoExperimentError < NameError
+  end
+
 end

lib/vanity/playground.rb

@@ -95,10 +95,11 @@ def define(name, type, options = {}, &block)
     # an exception if it cannot load the experiment's definition.
     #
     # @see Vanity::Experiment
+
     def experiment(name)
       id = name.to_s.downcase.gsub(/\W/, "_").to_sym
       warn "Deprecated: pleae call experiment method with experiment identifier (a Ruby symbol)" unless id == name
-      experiments[id.to_sym] or raise NameError, "No experiment #{id}"
+      experiments[id.to_sym] or raise NoExperimentError, "No experiment #{id}"
     end
 
 

test/experiment/ab_test.rb

@@ -234,7 +234,7 @@ def test_destroy_experiment
   # -- A/B helper methods --
 
   def test_fail_if_no_experiment
-    assert_raise NameError do
+    assert_raise Vanity::NoExperimentError do
       get :test_render
     end
   end

test/experiment/base_test.rb

@@ -34,7 +34,7 @@ def test_fail_when_defining_same_experiment_twice
   # -- Loading experiments --
 
   def test_fails_if_cannot_load_named_experiment
-    assert_raises NameError do
+    assert_raises Vanity::NoExperimentError do
       experiment(:ice_cream_flavor)
     end
   end