I tested this in a local git branch.
UPDATE: Looks like packages/libs are excluded from the git config. So if you do this, you'll need to return to your original branch and run> bower install to restore the bootstrap css
Remove the dependency to bootstrap from your bower.json file.
Then run> bower uninstall bootstrap
This should clear it up. Last thing I think you would need to do is remove the include from your app template html file. Bower may support Zurb, I didn't look. See if you can add the dependency to your bower.json and run> bower install
(PS. I'm new to meanjs, but that's how I would approach this scenario.)