Fixing: Pygpu init function doesn't process opencl device

Sending pull request for the [issue](https://github.com/Theano/libgpuarray/issues/20)
Will this accept something like "opencl0:22".  It's sort of less important for the platform part (the first int) because I don't anticipate a lot of machines with more than 9 platforms, but for the device part, I am pretty sure that limiting to 9 or less is bad.