Merge pull request #2 from leonardowf/master

Adds public initializer to NetworkActivityPlugin

Author: DenTelezhkin

Diff for: Source/Core/NetworkActivityPlugin.swift

@@ -42,6 +42,8 @@ public class NetworkActivityPlugin : Plugin {
         }
     }
 
+    public init() {}
+    
     public func willSendRequest(request: NSURLRequest?) {
         self.dynamicType.networkActivityCount++
     }