Introduce the Both[T] class
Use Both in CommitmentNotification
Use Both[T] for Deposits
Introduce MockMicroPaymentChannel
Fix timer cancellation

 * Make AkkaSpec and BitcoinjTest afterAll methods compatible to allow
   timer cancellation
 * Remove some dead code related with timers

This change fixes #189
Replace ProtoMicroPaymentChannel in BuyerMicroPaymentChannelActor
Merge pull request #205 from sortega/issues/41

Last preparations for replacing ProtoMicroPaymentChannel with MicroPaymentChannel