Recorder tweaks

Hey @luandro I've made a couple of minor changes to the code in the Recorder:

• changed the state to use e.g. isPaused instead of paused (convention to signal a boolean state)
• added isProcessing so user knows when saving is happening
• extracted a mini RecButton component to tidy code
• changed the render() to display different set of buttons at different times (makes it a lot clearer):
  • recording : Record, Pause, Stop
  • processing : just a "processing..." message
  • finished : Play