Refactoring pairwise into pairwise and gemm

The pairwise benchmark was contaminated by gemm-based solutions. I made a gemm benchmark dir, which tests the ability of various compilers to compete with BLAS libraries, and removed the gemm-based solutions to the pairwise benchmark. Currently the BLAS libs destroy the compiled functions, but I am curious if a readable Python base implementation that actually exposes a fast blocked algorithm could be compiled to run at a more competitive speed.

For the pyopencl stuff, I moved it to a new repo (https://github.com/jaberg/python-benchmarks-pyopencl) because I am interested in developing pyopencl auto-tunable code generators, and development along that line should not clutter up this repo.