ENH: Implemented ma.append

Fixes #2219.
MAINT: Remove doc/numpybook.

Remove doc/numpybook. It has become outdated in parts and its contents
is now part of the official numpy documentation.
DOC: Document removal of doc/numpybook in 1.9.0 release notes.
ENH: add extended axis and keepdims support to median and percentile
Merge pull request #4339 from abalkin/issue-2219

ENH: Implemented ma.append
MAINT: revert back to separate median implementation

Merging median and percentile make would break astropy and quantities as
we don't call mean anymore. These packages rely on overriding mean to
add their own median behavior.
Merge pull request #3908 from juliantaylor/median-percentile

add extended axis and keepdims support to percentile and median
BUG: Fix commutativity of {dot,multiply,inner}(scalar, matrix_of_objs)

Fixes #2469 and #4482. Relaxes fail condition to allow subtype as documented.
Merge pull request #4488 from charris/remove-numpybook

MAINT: Remove doc/numpybook.
DOC: Change pyrex to Cython in c-info.how-to-extend.rst.
Merge pull request #4493 from charris/reference-cython-not-pyrex

DOC: Change pyrex to Cython in c-info.how-to-extend.rst.
doc fixes to 'array-protocol type strings'

The item size is not always used (and not always means exact bytes), and
'O' was not in the table.
explain character codes of dtype.kind

"one of 'biufcSUV'" is not very helpful if it stands alone,
also the 'O' typecode was missing.
"(byte-)string" in PyArrayInterface.typekind docs
ENH: release gil for indexing operations

closes gh-4310
ENH: release gil for put and putmask
DOC: specify that 2d array must be non-empty in np.poly error message.

Fixes #2092. Changes message passed to ValueError.
Merge pull request #4067 from hmeine/master

explain character codes of dtype.kind
Merge pull request #4498 from meltingwax/meltingwax/2092

DOC: specify that 2d array must be non-empty in np.poly error message.
Merge pull request #4497 from juliantaylor/index-gil-release

ENH: release gil for indexing operations