Iterate functionality, no tests yet
Iterate functionality fixes related to callback misuse
Updated docs to support iterate feature
Merge branch 'master' of github.com:mozilla/localForage into iterate

Conflicts:
	dist/localforage.min.js
	dist/localforage.nopromises.min.js
	site/localforage.min.js
Tidy up code nits
Tweak API docs for iterate
Add `iterate` to CHANGELOG