Enable DOM storage and database APIs in WebView
Merge pull request #3 from ribot/feature_enable_storage

Enable DOM storage and database APIs in WebView
Fix duplicate listener issue by changing ArrayList to HashSet
Merge pull request #6 from ribot/fix_duplicate_listeners

Fix duplicate listener issue by changing ArrayList to HashSet
Makes Pig thread safe
Merge pull request #7 from ribot/fix_concurrency

Makes Pig thread safe
Allow calls to execute with no callback on Android

Sometimes you may wish to make a call to Javascript with either no
callback or a null callback, if you don't care about the response.

If there is no callback, `-1` is sent to Javascript as the key and
then it will not try and send messages over the bridge.
Merge pull request #9 from ribot/feature_no_callbacks

Allow calls to execute with no callback on Android
Fail when more than one response is sent from the response object

Throws an error when more than one call to either `success` or `fail`
is made on the response object.

Fixes #4