ENH: improve stats.nanmedian more by assuming nans are rare

Move nans to end of array instead of creating a new array without them.
This is faster under the reasonable assumption that nans are rare.
ENH: add runtime warning for all nan slice of nanmedian
MAINT: use assert_warns instead of a more complicated mechanism
MAINT: copypaste assert_warns from a newer numpy into scipy
MAINT: move a numpy compatibility function into its own file
MAINT: python 3 compatibility boilerplate
ENH: change to use array view in signal/_peak_finding.py
MAINT: tools: add a script that produces a list of closed github tickets for a miletone
MAINT: tools: update author list tool
DOC: release: update autogenerated lists in 0.14.0 release notes
DOC: fix some minor issues in 0.14.0 release notes.
Merge branch 'pr/3415' into master.

Review at https://github.com/scipy/scipy/pull/3415
REL: set version to 0.15.0-dev, add 0.15.0 release notes.
BUG: tools: Fix list of FMA instructions in detect_cpu_extensions_wine.py
DOC: stats: Add 'entropy' to the stats package-level documentation.
Merge pull request #3420 from WarrenWeckesser/doc-stats-entropy

DOC: stats: Add 'entropy' to the stats package-level documentation.
Merge pull request #3419 from WarrenWeckesser/fix-fma-instructions

BUG: tools: Fix list of FMA instructions in detect_cpu_extensions_wine.py
Added 'eps' in optimize.show_options for L-BFGS-B

In scipy.optimize.minimize, when algorithm is L-BFGS-B, there is an
option called eps. However, this options is missing if we use
scipy.optimize.show_options('minimize', 'L-BFGS-B') to look up its
options.
Merge pull request #3427 from yw5aj/master

Added 'eps' in scipy.optimize.show_options for L-BFGS-B
MAINT: Add myself to thanks :)

I worked on scipy.sparse a bit last summer for GSoC.
Thanks again @pv!