Great. I just figured out how to install the M highlighting into Sublime Text 2.
Basically, sublime text is the text editor and apparently all these text editors are pretty powerful (emacs, etc).
For sublime text 2, there is a package installer and manager so you need to have that installed first via https://packagecontrol.io/installation. Then the next step is to add the repo (https://github.com/ksherlock/MUMPS.tmbundle) by using the instructions at this page: https://packagecontrol.io/docs/usage. Then install the package with the direction on the same page (https://packagecontrol.io/docs/usage) under install package. Make sure to read the blurb about basic functionality first for commands to connect to the github repository and then actually installing it. To check that it worked on sublime text, click on the bottom write where it says “plain” or whatever language it’s currently set to and MUMPS should be an option.