* Alterations made following the recent refactoring.

* New rtworksteal files added which implements the render thread algorithm presented
  by McGuiness. A new rule has been added to the Makefile to allow us to build this version without the other
  implementations files.

* mandelbrot.c is now independant from any work-stealing implementation. In order to implement a scheduling scheme
  there are a few interface functions to implement and it works a treat!

* Deque implementation is now fixed. The cas function is now removed and simply replaced with a pthreads mutex.