Pinning our Sphinx documentation versions.

[rdegges]

This commit will also ensure the docs building stuff isn't part of the npm package, etc.

This will help to resolve future documentation search issues by pinning our Sphinx release.

[coveralls]

Coverage remained the same at 68.536% when pulling c016dc647000f2f83566cd373385a9afef04ddfb on docs-update into 3b242a09b174d4a7e70fb7a9820bc0531703a2ee on master.