Also:
- In the getting started guide, the TFE content was all tailored to the older
run-locally workflow. I've replaced it with some brief explanation and a link
to the dedicated TFE getting started guide.
- Fixed a sidebar link glitch in the configuration section. (Both "Terraform"
and "Terraform Enterprise" were marked as active if you were on the TFE page.)
- Renamed the "Terraform Enterprise" page "Terraform Push." (Some people have
gotten confused and landed on this page when trying to set up the `atlas`
remote backend.)