As The M Project is built on JavaScript / NodeJS any standard code editor will do.
Here at Wherewolf
http://wherewolf.co.nz/ where most of our projects are built using TMP, we use Sublime Text
http://www.sublimetext.com/ though our devs are free to use whatever they feel most comfortable with (Dreamweaver's code editor & Vim included). Sublime Text runs on Win/Mac/Linux and one very great feature of Sublime Text is the package management / plugins offered, allowing you to install great tools that do things like autocomplete variable/function names, highlight extra whitespaces, automagically run your code through JSLint, search across a whole project, rename vars across the whole project...