BLD: Don't import the pandas test helper "assert_index_equal()", which is currently unavailable in stable release.
WIP: try_numba_autojit() now accepts keyword arguments (to support numba refine)
Further numba refine speedups.

- Removed indirect loading of "neighborhood" and "raw_neighborhood," which included use of slicing.
- Made 'square' into 2 scalars with declared types.
Added more-demanding benchmarks for numba feature code.
BUG: "invert" option to locate() broken. Added test and fixed.
Merge pull request #51 from nkeim/numba-refine

Further numba speedups; incidental bugfixes