Split distributions

[argriffing]

Break the distributions.py file into three files. The scipy tests all pass for me, and I guess we will find out if they pass on Travis. The docstrings are built on the fly and I do not think this docstring generation code is tested.

[argriffing]

One of the Travis builds failed because pypi didn't provide mpmath in a timely manner

Downloading/unpacking mpmath
HTTP error 503 while getting https://pypi.python.org/packages/source/m/mpmath/mpmath-0.17.tar.gz#md5=e27af3a77bc39c8745d5d1c09a8247ac (from https://pypi.python.org/simple/mpmath/)

I'll check if closing the PR and re-opening will make Travis retry downloading mpmath.

[coveralls]

Coverage remained the same when pulling 83e61ea on argriffing:split-distributions into 47f10f7 on scipy:master.

[WarrenWeckesser]

I haven't looked too closely at this yet, so I have just a quick initial comment: all the new files should be "private" modules (i.e. give the filenames an underscore prefix). We're trying to avoid the proliferation of public submodules, so unless there is a compelling reason, the default should be "private" for new modules.

[argriffing]

I deliberately used discrete_distns and continuous_distns without underscores, with the idea that they could be imported as part of the public interface, for example if someone wanted only continuous or discrete distributions. The __all__ list of the original distributions module is now cleanly divided between them. I gave the third module an underscore prefix because it should not be part of the public interface.

But if this is not a good idea then I will give them underscores.

[rgommers]

I'd rather not have more public modules. We already have stats.norm and stats.distributions.norm, which is one too many.

[josef-pkt]

I'm not sure this PR works.

You need to copy paste, delete add in the same commit to preserve git history.

Without blame it will be very painful to "maintain" distributions.

[argriffing]

OK, I've added underscore prefixes to the submodules.

[argriffing]

I'm not sure this PR works.
You need to copy paste, delete add in the same commit to preserve git history.
Without blame it will be very painful to "maintain" distributions.

Closing, with the idea to make a new PR that is less awkwardly gitted

[coveralls]

Coverage remained the same when pulling 861f624 on argriffing:split-distributions into 47f10f7 on scipy:master.