ENH: Refactor refine to use numba if avaiable. Add enable/disable tools.

WIP Good in Python but not in numba. Loop moved inside.

WIP: _refine compares and locate returns results. Nosetests error.

WIP: Comment out memo decorators. Smoke test runs without error.

WIP: Mute llvm DEBUG logging.

WIP: Reinstate memoization.

WIP: Wrap _refine in Python-friendly refine.

WIP: Whole pixel test fails but does not error.

WIP: Updating slice does not break code but whole pixel tests is still wrong.

WIP new_coord is just a reference to coord, no need to declare it

WIP: Add try_numba_autojit and run tests with and without.

WIP: Skip numba tests if numba cannot be imported.

WIP: Try global state idea of Tom's.

WIP: enable and disable numba work.

WIP: Try import numba on trackpy import and never again.

WIP: More specific datatypes in _refine, trying to solve numba-only test failure.

WIP: Replace simple dict with RegisteredFunction class.

Fixed typo that reversed enable and disable

Fixed two bugs and added outfile stuff.

WIP: Replace magic-number thresholds with constants. Not broken.

Use more numpy.

Lower good enough threshold -- float64 was the culprit.

WIP: Removed outfile stuff

WIP: Use shape to set upper bound.

Set Travis nosetests not to capture log -- won't matter for now