Verify coho npm-link works through createmobilespec

Right now, several of us have npm-link issues when trying to use createmobilespec. Needs to be tested on a clean repo clone.

`coho npm-link` steps needs to be verified and made reliable, if possible.
I know there are issues with npm link, perhaps test also with the new `--use-yarn` option, although in my tests yarn had problems as well, but need to verify.