Safari 7.1+ IndexedDB is equally buggy as iOS 8+

In PouchDB we found Safari 7.1 and 8 to have the same issues cited in the article about iOS 8. For more details:

* https://github.com/pouchdb/pouchdb/issues/2533
* https://github.com/yathit/ydn-db/issues/20
* https://github.com/mozilla/localForage/issues/254
Merge pull request #817 from nolanlawson/patch-1

Safari 7.1+ IndexedDB is equally buggy as iOS 8+