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
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
MAINT: some code cleanup in scipy.constants.

- rewrapped text in constants.codata
- capitalized "UK"
- verified the expression for atomic unit of permittivity
BUG: correlate was extremely slow when in2.size > in1.size
STY: PEP8 fixes for signaltools test (partially autopep8)
TST: Add a test for swapping of inputs
when in2 is bigger than in1, test reversal in 3 dimensions and complex conjugation
WHT: signal: more pep8 in tests
ENH: scipy.special: Improving sph_harm function
Rewriting the function in Cython using a different routine, thus improving the speed and precision of the function

Adding backward compatibility to sph_harm for double type m and n
GEN: scipy.special: regenerated ufuncs