Add recorder and playback

package.json

src/components/asset-panel/asset-panel.jsx

src/components/record-modal/meter.jsx

src/components/record-modal/playback-step.jsx

src/components/record-modal/record-modal.css

src/components/record-modal/record-modal.jsx

src/components/record-modal/recording-step.jsx

src/components/record-modal/waveform.jsx

src/containers/playback-step.jsx

src/containers/record-modal.jsx

src/containers/recording-step.jsx

src/containers/sound-tab.jsx

src/lib/audio/audio-buffer-player.js

src/lib/audio/audio-recorder.js

src/lib/audio/shared-audio-context.js

src/reducers/modals.js