Lighthouse Lambda Versions Save

• feat: use Headless Chrome 67.0.3396.87 (#20)

• feat: use lighthouse v3 (#19)

• docs: update README for v2

There is no major difference between v1.1.5 and v2.0.0. We create version 2.x so that lighthouse-lambda has the same major version of lighthouse.

• feat: use Chrome 67.0.3396.79 (#14)

• feat: use Chrome 67.0.3396.62 (#9)
• feat: save results to compare between versions
• feat: add option to save artifacts

• feat: use Chrome 66.0.3359.181 (#8)

• feat: use Chrome 66.0.3359.170 (#7)

• feat: allow to create html report from results (#6)

• feat: use Chrome 66.0.3359.139