fix js deps logic

[nick1udwig]

Problem

Resolves #55

Solution

std::process::Command doesn't have any memory between calls, so need to do the nvm use and whatever other operation in the same Command. The nice thing about this is we don't have to track the original node in use by the user: it'll get reset by itself.

Docs Update

N/A: functionality just works now, interface didn't change.

Notes

None.