Added support for Android and Android example project. Updated README, added checked in TestFlight SDK versions

Tested with and locked plugin.xml at Cordova 3.10 for Android.

Test code for CLI install

```
cordova create myApp

cd myApp/

cordova platform add android

cordova -d plugin add <path to plugin>

cordova build android
```

Test code for index.html

```
<body>
        <div id="container">
            <h1>TestFlight Plugin</h1>
            <section class="dialog">
                <p>Start TestFlight Plugin...</p>
                <button onclick="takeOff();">Take Off</button>
                <p>Send a custom checkpoint...</p>
                <button onclick="passCheckpoint();">Pass Checkpoint</button>
            </section>
        </div>
        <script type="text/javascript" src="cordova.js"></script>
        <script type="text/javascript" src="cordova_plugins.js"></script>
        <script type="text/javascript">
            var testflight;

            document.addEventListener('deviceready', function () {
                testflight = new TestFlight();
            }, false);

            function takeOff() {
                testflight.takeOff(null, null, 'insertKey');
            };

            function passCheckpoint() {
                testflight.passCheckpoint(null, function (err) {
                    alert("TestFlight Error: " + err);
                }, 'checkpointTest');
            };
        </script>
    </body>
```