BLD: add numpy requirement to metadata if it can't be imported.

This should help Buildout users.  Closes gh-3379.
Corrected the theilslopes implementation and added a test
Moved implementation to `stats.theilslopes`. Added tests to `stats`.
Added y ties term to the confidence interval calculation.
PEP8 fixes
BLD: add minimum required numpy version to build_requires if numpy not found.
MAINT integrate/odepack: kill dead Fortran code
MAINT: minor cleanups to stats.theilslopes.

Add complete references, reST formatting, PEP8, etc.
DOC: add example for stats.theilslopes.
DOC: remove docstring of stats.mstats.theilslopes, use stats version.
DOC: added notes about example for stats.theilslopes. Changed example wording.
Minor changes to docs for stats.theilslopes
BLD: ignore pep8 E302 (expected 2 blank lines, found 1)
BUG: correlate was extremely slow when in2.size > in1.size
Merge pull request #3661 from argriffing/ignore-e302

BLD: ignore pep8 E302 (expected 2 blank lines, found 1)
Merge pull request #3609 from larsmans/cleanup-odepack

MAINT: integrate/odepack: remove unused Fortran code
Merge pull request #3566 from rgommers/buildout-stupidity

BLD: add numpy requirement to metadata if it can't be imported.
Merge pull request #3574 from tomflannaghan/theilslopes-fix

Fixes multiple bugs in mstats.theilslopes
MAINT: some code cleanup in scipy.constants.

- rewrapped text in constants.codata
- capitalized "UK"
- verified the expression for atomic unit of permittivity
Merge branch 'pr/3585' into master.

See https://github.com/scipy/scipy/pull/3585