support more datetime64 and timedelta dtype variants
make nanops._maybe_null_out work with complex numbers ( issue #7353 )
support axis=None for nanmedian ( issue #7352 )
make nanops work when ndim==1 and axis==0 ( issue #7354 )
Make nanops._has_infs work for additional dtypes and multidimensional arrays ( issue #7357 )
also disallow timedeltas for objects that disallow datetime64
remove warning about coercing complex values
add tests for nanops
minor nanops pep8 fixes