[now-cli] Install dependencies before running now dev in tests (#2948)

* [now-cli] Install dependencies before running `now dev` in tests

* Check install exit code

* Add more logging

* Add more logging

* More logging

* Include yarn.lock file

* Add lock files to dev fixtures

* Ignore test

* Ignore another test

* Ignore another test

* Whitespace

* Install deps for unit tests

* Whitespace

packages/now-cli/test/dev-builder.unit.js

@@ -1,5 +1,4 @@
 import test from 'ava';
-
 import { filterPackage } from '../src/util/dev/builder-cache';
 
 test('[dev-builder] filter install "latest", cached canary', async t => {