major refactor to implement a MVC structure

Even though this started as a simple application, the code started
to become too tightly coupled.  Since it is still early in the
development, I decided to do a refactor to implement a MVC structure.

* moved the main method to App.java, which will act as the main
  class and instantiate all other objects--the model, view
  and controller.

* changed TimerFrame.java to TimerFrameView.java.  This file only
  deals with the swing components and the custom ButtonPanelView.

* changed ButtonPanel.java to ButtonPanelView.java.  This is to
  reflect that this class acts as a view.  Removed the
  actionListener from this class and moved it to the controller.

* created a controller class, which implements the actionListener
  and assigns it to each of the buttons.  The controller gets the
  view as a contructor paramater and is then able to get access to
  the buttons.  The conroller also get a reference to the view
  through the constructor.

* changed Timer.java to TimerModel.java to indicate that it serves
  as the model for this application.  It knows nothing of the view
  or controller.
Merge branch 'master' of origin

Did not git pull prior to last commit. Forgot there was a change
to the .gitignore file--ignoring the .c9 configuration directory
for development on the cloud 9 IDE.  Merging remote commit now.