Update CONTRIBUTING.md

updated JSFiddle/JSBin to 1.0.0-rc.2
Fix typo in {{partial}} docs.
Merge pull request #2411 from xtian/partial-docs-typo

Fix typo in {{partial}} docs.
Merge pull request #2406 from craigteegarden/patch-1

Update CONTRIBUTING.md JSBin/JSFiddle to 1.0.0-rc.2