refactor(localforage): create a constructor for the localforage object
feat(localforage): add support for multiple storage instances
test(localforage): add tests fot multiple storage instances support
Cast non-string keys to strings (fix #250)
Warn if casting key to string (#250)
fix(test.api): fix PhantomJS - SECURITY_ERR on multiple instances tests
fix(localforage): fix localStorage fallback, when webSQL driver fails
Merge pull request #253 from thgreasi/instances2

feat(localforage): add support for multiple storage instances
Merge pull request #257 from mozilla/250-setkey-undefined

Cast non-string keys to strings (fix #250)
Use error-first callbacks (close #219)
Use `err` not `error` for consistency's sake
Merge pull request #256 from mozilla/219-error-first-in-callbacks

Use error-first callbacks (close #219)
Normalize bad config values across platforms

* fix #243
* fix #247
Tweak README for config fix