Update README.md

Better instructions for people who just want to run it locally
Update package.json so `npm start` will work
Merge pull request #23 from jugglingnutcase/patch-1

Update package.json so `npm start` will work
Merge branch 'vNext'
Extend timeout for image optimization test
Merge pull request #30 from kraken-io/fix-timeout

Extend timeout for image optimization test
Merge branch 'master'