v0.5.6 Release

[caseykneale]

So I fixed a few bugs, namely bugs in plots, and I refactored some code and docs.
This is mostly a test to see how the automatic review process works for minor versions,

@JuliaRegistrator register()

[JuliaRegistrator]

Registration pull request created: JuliaRegistries/General/4091

After the above pull request is merged, it is recommended that a tag is created on this repository for the registered package version.

This will be done automatically if Julia TagBot is installed, or can be done manually through the github interface, or via:

git tag -a v0.5.6 -m "<description of version>" c1027381847a5890f8a0ef980f9bf8ef6e087efa
git push origin v0.5.6