Hi Matt,
Working on the bleeding edge build may not be a recommendable practice.
Here's how you do it though:
To run TiddlyWiki on node with your fork of the repo, you simply open a command prompt in the repo folder and do:
npm link
From now on, node will use your local fork running any tiddlywiki commands like:
tiddlywiki --server
If you want to switch back to using the latest release, you simply run this in the console:
npm install -g tiddlywiki
I use the last release as the build env for my plugin repo and the latest build, of course, when doing core development and making pull requests against any feature branches I created based on master.
Hope that helped.
best wishes
-tb