AGCORDOVA-36 : add support for Android < 4.4

Due to lack of Promises support in webview Android < 4.4 and the responseType:"json" bug http://stackoverflow.com/a/9845704/3860046. This PR make it compatible again.

Should go in master and 1.0.x 

Please to on Android 4.4 and below, and also ios.

@edewit @lfryc @matzew  Can you test and merge ? 

Here is the PR: https://github.com/sebastienblanc/aerogear-pushplugin-cordova/pull/1