Only count conversions for participants (or implicit conversions)

This makes it so the "total conversion count" (as opposed to unique converted participant count) will only be tallied for participants (or implicit conversions), thus making it behave similarly to how unique participant conversions are tallied.
Coincidentally, also fixes active record conversion counting (previously it treated conversions as implicit even though the argument defaults to false).

lib/vanity/adapters/active_record_adapter.rb

@@ -276,9 +276,9 @@ def ab_add_conversion(experiment, alternative, identity, options={})
         implicit = !!options[:implicit]
         metric_id = options[:metric_id] # unsupported for ActiveRecord
 
-        VanityParticipant.retrieve(experiment, identity, false)
-        VanityParticipant.retrieve(experiment, identity, implicit, :converted => alternative)
-        VanityExperiment.retrieve(experiment).increment_conversion(alternative, count)
+        if VanityParticipant.retrieve(experiment, identity, implicit, :converted => alternative)
+          VanityExperiment.retrieve(experiment).increment_conversion(alternative, count)
+        end
       end
 
       # Returns the outcome of this experiment (if set), the index of a

lib/vanity/adapters/mongodb_adapter.rb

@@ -234,14 +234,14 @@ def ab_add_conversion(experiment, alternative, identity, options={})
             },
             :upsert=>true
           )
-        end
 
-        @experiments.find(:_id=>experiment).find_one_and_replace(
-          {
-            "$inc"=>{ "conversions.#{alternative}"=>count }
-          },
-          :upsert=>true
-        )
+          @experiments.find(:_id=>experiment).find_one_and_replace(
+            {
+              "$inc"=>{ "conversions.#{alternative}"=>count }
+            },
+            :upsert=>true
+          )
+        end
       end
 
       def ab_get_outcome(experiment)

lib/vanity/adapters/redis_adapter.rb

@@ -223,9 +223,8 @@ def ab_add_conversion(experiment_id, alternative, identity, options={})
 
           if implicit || participating
             @experiments.sadd "#{experiment_id}:alts:#{alternative}:metric:#{metric_id}:converted", identity
+            @experiments.incrby "#{experiment_id}:alts:#{alternative}:metric:#{metric_id}:conversions", count
           end
-
-          @experiments.incrby "#{experiment_id}:alts:#{alternative}:metric:#{metric_id}:conversions", count
         end
       end