DOC: add isclose and partition to reference and link some docs

also drop sometrue/alltrue link, its equivalent to any/all.
Merge pull request #3744 from juliantaylor/doc-update-1.8.x

Backport PR 3741
MAINT: Move FutureWarning in nansum.

Currently a FutureWarning about the sum of empty slices changing to zero
is always raised. Instead make it depend on the actual occurrence of an
empty slice.
BUG: use correct type for hash values

As of Python 3.2 hash values are of type Py_hash_t. Previous versions use C long.
TST: Test that FutureWarning is not raised by nansum if not all-nan.
Merge pull request #3745 from charris/move-nansum-warning-in-1.8

Move nansum warning in 1.8
Merge pull request #3749 from charris/backport-1.8-3747

Backport 1.8 3747