Cleanup client.speaker and add additional tts speakers (svox-pico-tts and google-tts)

Also, get rid of aplay and use pyaudio instead (pyaudio is a dependency anyway, so why rely on an external tool that might not be installed)
Rename isAvailable() to is_available()
Added slugs to TTS engines
Improve is_available method
Actually include a phrase in eSpeakSpeaker.say()
Added logic to select the TTS engine from a slug
Getting tts engine from profile
Added missing import
Remove unused import
Add yaml import to speaker.py
Use slug in Exception
Added __main__ testing code to client/speaker.py
Simplify is_available() method of osx-speaker
Fix missing brackets in speaker.py testing code
Change AbstractSpeaker.play() to use aplay due to issues with PyAudio playback

see jasperproject/jasper-client#188 for more info
Change AbstractMP3Speaker.play_mp3() to use AbstractSpeaker.play()
Add better TTS engine detection/testing code
Use distutils.spawn.find_executable instead of which
Use os.devnull instead of hardcoded /dev/null
Added logging system to client/speaker.py