Ignore decodeURIComponent errors in auth parsing + README touchups

For when the URL's auth carries a percent sign not intended to escape: http://first%[email protected]

Fix headers in the README. Also give grammar and spelling a once-over.

The reformatting on line 755 in src/urlparser.js is to shut lint up.