DOC: change example sample spacing

Change the sample spacing in the example so the linear interpolation points line up with the original points
TST: stop shadowing ellip* tests vs boost data
TST: silence warning from testing optimize.curve_fit with infs.
TST: clean up optimize tests (no test docstrings, Github issue numbers).
TST: silence test warnings for invalids for stats.nanmean/nanstd.
Merge pull request #4263 from rgommers/clean-testnoise

MAINT: clean up test noise and optimize tests for docstrings and Trac issue numbers
DOC: Interpolation example, Add num=11, 41

and change shape so it still shows the interpolation clearly

[ci skip]
Merge pull request #4242 from endolith/patch-5

DOC: change example sample spacing
Merge pull request #4253 from ev-br/ellip_tst

TST: stop shadowing ellip* tests vs boost data
MAINT: remove NumPy < 1.6 compatibility