[voice] add google voice support

voice/voice_factory.py

@@ -0,0 +1,17 @@
+"""
+voice factory
+"""
+
+def create_voice(voice_type):
+    """
+    create a voice instance
+    :param voice_type: voice type code
+    :return: voice instance
+    """
+    if voice_type == 'xfyun':
+        from voice.xfyun.xfyun_voice import XfyunVoice
+        return XfyunVoice()
+    elif voice_type == 'google':
+        from voice.google.google_voice import GoogleVoice
+        return GoogleVoice()
+    raise RuntimeError