Docs update

[decarlof]

This pull request only affects build files (meta.yaml and setup.py) and docs folder.

docs build fine on linux but on readthedocs fail to create links to functions.

I think is because conda build still fails the test (missing conda install for phasepack and cached-property) and/or doc headers in some functions have error.

Since here I am only touching meta.yaml, setup.py and docs folder please keep this pull request open till the conda build is solved.

[carterbox]

I think phasepack and cached-property are only available through pip. I don't know how that effects our conda distribution.

[decarlof]

@carterbox I had to simply pip install before installing with conda and to get the doc to build add them both in the mock section of the conf.py file. After this the docs builds nicely on linux will all API function fully linked but still fails on mac and on read the docs site. I noticed some minor errors in the comment section of several functions, perhaps mac/readthedocs are more strict but I did not want to edit the xdesign python functions since you are still very active. I can do this at a later time.