Gut console reporting of ephemeral rejections

Fixes #474
Update copyright in README.md
Update copyright range in license
Support Chrome CSP’s without unsafe-eval

By using a different check for existence of SpiderMonkey generators
instead of existence of ES6 generator syntax support.

Fixes #480
Post version policy prominently
Merge pull request #481 from kriskowal/gh-480

Support Chrome CSP’s without unsafe-eval
Merge pull request #478 from kriskowal/no-console

Gut console reporting of ephemeral rejections