traversing: Optimise .add by not using makeArray

Closes gh-1430
Doc: Update links and simplify build instructions
Update grunt-bowercopy to 0.5.0
README: Add jQuery environment notes
Docs: Link to the browser support page in CONTRIBUTING.md

Instead of duplicating the supported browsers matrix, just link to
the browser support page on jquery.com.
Effects: First step() call should match :animated selector

Fixes #14623
Closes gh-1473