Numpy docs hmc

[ColCarroll]

As was foretold in #2403

@aseyboldt you might take particular offense to some of the docstrings -- would love any nitpicks.

[ColCarroll]

(also, removing attribution to @jsalvatier is not meant as a slight -- I think the git history provides a record of credit, and this is interpreted by numpy as a malformed module docstring.)

[junpenglao]

what is this for?

[ColCarroll]

I'll add a comment -- D100 wants a docstring at the top of every file, and D104 wants a docstring in every __init__.py file

[aseyboldt]

stopping time and step size adaptation.

[aseyboldt]

The standard says that we shouldn't document the arguments in __init__ and in the class doc string.
https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt#class-docstring

[ColCarroll]

It looks like most of the class doc string is documenting the sampler_stats return object -- I hadn't seen that there is an Attribute section for class docstrings though, which is probably where the sampler stats should go...

[ColCarroll]

Actually, that is a funny thing to document in __init__ since it is an attribute it provides on the trace object. It makes sense to me to leave it where it is, and not adding an Attribute section.

[aseyboldt]

Thanks for writing all those doc strings!

[ferrine]

Don't we want new line after """?

[ferrine]

Numpy should be imported before local imports by pep8

[ColCarroll]

I updated this here -- it is actually a pylint check (wrong-import-order) that I can maybe try adding tomorrow, but that is a ton of violations!

[ColCarroll]

Going to merge these once tests pass, since the rebasing is a pain and just making sure that the docs follow the functions around!

[twiecki]

This is great @ColCarroll.