Decoupling SBWindow from SBBark (handling the github issue and mail feedback). Allowing to call bark by itself ([[SBBark sharedBark] showBark]) and give more flexibility to invoke Bark.
Also SBWindow become more generic (dispatch a NSNotification) and can be use by other class to handle shake event (as [SBBark sharedBark] still support a delegate to verify if it should present).