RESTClient does not support ULAW file upload

[matthewmgamble]

When attempting to use the speech API with a raw ULAW file (which is supported according to the API docs) the upload fails because the content type is not set:

        {"RequestError": {
         "ServiceException": {
         "MessageId": "SVC0002",
         "Text": "Invalid input value for message part %1" ,
         "Variables" : "Content-Type"}
        }}

Looking at RESTClient.java, it appears the client only checks for WAV, Ogg, and AMR file types and if it does not find one of those it leaves the content type as null.

There are two possible fixes for this - let the user override the content type when setting the source file in the SpeechService API, or update the logic in RESTClient.java to support setting the audio/raw mime types supported by the API. The only challenge would be detecting the rate and byteorder.