Add test for stdin.isTTY in assign.js
Add test for stdin.isTTY in assign.js

It looks like streams that aren't run inside a text terminal ("TTY")
context have problems with process.stdin.setRawMode(true). So this
should make sure that it's only set if the stream is a TTY.

trolster/urcli,gabraganca/ur-cli,trolster/ur-cli