Using type suffix

Fixing CompilerWarning: <program source>: warning: double precision constant requires cl_khr_fp64, casting to single precision
An application that wants to use double will need to include the directive before any double precision data type is declared in the kernel code.

* Numpy does element-wise operations by default.  Updated the cpu
  operation to use pure numpy.

* Eliminated the loop which is not necessary to demonstrate
  parallelism on array operations.

* Made the number of workers explicit rather than gpu chosen,
  through local_size variable passed to kernel execution.

* Increased to ~8 million data points to more clearly demonstrate
  the difference between cpu and gpu based computations.

* Add a test suite.
* Fix numerous `get_info` bugs. (reports by David Garcia and the test suite)
* Add :meth:`pyopencl.ImageFormat.__repr__`.
* Add :meth:`pyopencl.addressing_mode.to_string` and colleagues.
* The `pitch` arguments to·
  :func:`pyopencl.create_image_2d`,
  :func:`pyopencl.create_image_3d`,
  :func:`pyopencl.enqueue_read_image`, and
  :func:`pyopencl.enqueue_write_image`
  are now defaulted to zero. The argument order of `enqueue_{read,write}_image`
  has changed for this reason.
* :meth:`pyopencl.MemoryObject.get_image_info` now actually exists.
* Add :meth:`pyopencl.MemoryObject.image`.