Add a synchronous method to MediaTranscoder

[ralphpina]

Currently, all transcodeVideo methods in MediaTranscoder are async methods. However, there are many situations where a synchronous method might be preferable. IntentServices and Handlers with their own HanderThread are two that quickly come to mind. Would you be open to a PR to add a synchronous method? I was thinking of pretty much copying/pasting the current work that transcodeVideo does, like so:

public void transcodeVideo(final FileDescriptor inFileDescriptor, final String outPath, final MediaFormatStrategy outFormatStrategy, final Listener listener) throws IOException, RuntimeException {
    MediaTranscoderEngine engine = new MediaTranscoderEngine();
    engine.setProgressCallback(new MediaTranscoderEngine.ProgressCallback( {
        @Override
         public void onProgress(final double progress) {
             listener.onTranscodeProgress(progress);
         }
    });
    engine.setDataSource(inFileDescriptor);
    engine.transcodeVideo(outPath, outFormatStrategy);
}

I figure that if you are running this synchronously you know what you are doing and you can handle your own Exceptions/failures. You'll know it was successful when it returned. The only listener call that you might be interested in is for progress?

[ypresto]

I have same issue on app which uses this library. Currently doing patch work with CountDownLatch...
I think it is good idea to provide sync version of methods.

Note that there are some reasons using async interface and thread pool:

• Cannot run in Thread with Looper (a.k.a. HandlerThread, IntentService)
• Use only one thread to keep from exhausting device resources

So sync version would be better to use same thread pool than async version.

[ypresto]

We're currently working on Future (#12). It also can be passed to Observable.from()!

[ypresto]

v0.1.10 returns Future. Please use Future.get() to wait for result synchronously!