DRAFT: Add Transonic + {Pythran, Cython}

[ashwinvis]

Fixes #9

Notes:

1. Calling the setup function multiple times in a benchmark should be avoided
2. Equation of state benchmark was easy to implement
3. Isoneutral benchmark has some issues -- does not compile yet, despite workaround in ba03d48
4. TODO: Turbulent kinetic energy benchmark

[ashwinvis]

cc: @serge-sans-paille and @paugier if you are interested

[dionhaefner]

:wave: @ashwinvis, thanks for the implementation. This looks really high quality. I'm just curious: could you share your experience with running the benchmarks through Transonic so far?