Finish WIP features

[Darko Kukovec]

There are some features in the add-additional-example-sources branch that should be finished and merged to master:

• Add verbose flag to squawk (e5522a9) - #39
• Support missing readme (e32693c) - #32
• Add timing output and check for extract plugin example (f5d1390) - #40
• Update readme (92f78ba) - #33
• Support yarn warnings in stderr (f1ca52f) - #43

Commits covered by other issues:

• Use yarn over npm for faster installs (f8bf6d3) - #21
• Reset package.json file after run (f898a12) - #22
• Correct direct webpack call command (6382caf) - #22