BUG: upcast weights to average result type to avoid inaccuracies

closes gh-5202
Merge pull request #5214 from mkowoods/np.average

Update to average calculation
ENH: support parallel compilation of extensions

Allow extensions using numpy.distutils to compile in parallel.
By passing `--jobs=n` or `-j n` to `setup.py build` the compilation of
extensions is now performed in `n` parallel processes.
Additionally the environment variable NPY_NUM_BUILD_JOBS is used as
the default value, if its unset the default is serial compilation.

The parallelization is limited to within the files of an extension, so
only numpy multiarraymodule really profits but its still a nice
improvement when you have 2-4 cores.
Unfortunately Cython will not profit at all as it tends to build one
module per file.
DOC: update installation instructions
BUG: fix not returning out array from ufuncs with subok=False set

closes gh-5240
Merge pull request #5242 from juliantaylor/fix-ufunc-subok-out

BUG: fix not returning out array from ufuncs with subok=False set
DEP: deprecate pkgload
MAINT: warn instead of raise
Merge pull request #5245 from argriffing/deprecate-pkgload

DEP: deprecate pkgload
Fix issue with fromarrays not correctly determining a format string for unicode data (in the process eliminate some unnecessary cruft)
Merge pull request #5251 from embray/astropy-3052

Issue with fromarrays not using correct format for unicode arrays
Merge pull request #5161 from juliantaylor/parallel-distutils

ENH: support parallel compilation of extensions