Refactor for v0.4 to better match distutils, reintroduce .dist

- Drop -march=native from 'fast' (see bjodah/pybestprac#5)
- Set -O2 instead of -O3 in 'fast'
- Drop `Olevel` and `march` kwargs to CompilerRunner (let user set those via flags instead)
- Reintroduce dist.py in order not to have to depend on pycodeexport for so many projects.
- Default render in .dist is not standard python string templating instead of mako (no ext. dep.)