Update documentation

[Shibabrat]

Merge unit test for differential correction method for the uncoupled system.

Initiate work on updating docs for methods.

Fixes #2, fixes #7, fixes #47, fixes #48

[JoshKarpel]

Could you make sure the build artifacts in docs/_build aren't checked in to git (docs/_build should be in your .gitignore)? Read the Docs will build from source anyway, and it makes the repo a lot less noisy. Same with ``build/` for package build artifacts.

Otherwise, LGTM!

[kthyng]

@dpsanders can you have a look at these changes? Thanks!

[dpsanders]

The docs are looking very nice! +1