added complex functions to npymath
fix previous merge
small refactor in scalar tests.
Merge remote-tracking branch 'origin/master' into npymath-complex
removed unneeded import in typeinfer
prefer relative imports
return None in numpy_letter_types_to_numba_types on unsupported types

more convenient than raising an error.
numpy ufunc type inference now fails for unsupported types

Also made a bit more uniform test_ufuncs.
removed spurious print
support testing ufunc loops in nopython mode
fixed doc: copysign is not supported yet in no python mode
ufunc loop test on all supported ufuncs.

Also fixed some bugs raised by enlarging the tests.
removed bool and complex types from the support as
they are not completely supported yet.
reenabled bool in numpy ufunc support; dict-based codegen for ufuncs
Merge remote-tracking branch 'origin/master' into npymath-complex

Conflicts:
	numba/_npymath_exports.c
	numba/numpy_support.py
	numba/tests/test_ufuncs.py
return -inf when numerator is negative and demominator is 0 in numpy div
use compile_isolated for tests
Improved class comment for TestLoopTypes (test_ufuncs.py)
tweak on unittets

- always run all the loops, report all failed ones on failure
- changed an ‘assertFalse’ on a known True to use the method ‘fail’
improved/corrected on doctoring for supported_letter_types.
fixed a typo