General fixes

I've bumped the gradle plugin versions, build tool version. 
Also I had to add  okhttp 1.6.0 and okhttp-urlconnection 1.6.0 because Picasso was raising an Exception. ( Detail [here](http://stackoverflow.com/questions/24125856/picasso-detected-an-unsupported-okhttp-on-the-classpath) )

At least, I am able to build it and working for me now. Thanks a lot for open sourcing it.  
Because Android Studion was raising an error while I'm looking around the codes. And I found a [similar problem](http://stackoverflow.com/questions/18505973/android-studio-ambiguous-method-call-getclass)  on stackoverflow and fixed it according to the accepted answer there. 

> I think it is a bug in Android Studio. As we know, Android Studio is based on the IntelliJ Platform and the existing functionality of IntelliJ IDEA Community Edition.
>
> Google has developed it in cooperation with JetBrains. And same bug is reported to happen in IntelliJ as well. Have a look at the Error report
>
> However a workaround to this issue is:
>
> Casting the getClass() call to Object as follows:
>
> ((Object) this).getClass()