correcting supported types error

* removed opus qualifier from ogg/opus
* added mp3

This should probably be either generated automatically or else dropped. Or at least retrieved from the content-type file. But this is good enough for now.

Author: nfriedly

speech-to-text/file-player.js

@@ -66,7 +66,7 @@ function getContentTypeFromFile(file) {
       if (ct) {
         resolve(ct);
       } else {
-        var err = new Error('Unable to determine content type from file header; only wav, flac, ogg/opus, and webm are supported.');
+        var err = new Error('Unable to determine content type from file header. Supported file types: wav, mp3, flac, ogg, and webm.');
         err.name = FilePlayer.ERROR_UNSUPPORTED_FORMAT;
         reject(err);
       }