Electron v3.0.0 applyConstraints

Added APPLY button to test 'MediaStreamTrack.applyConstraints' api and change the resolution of a previously created media stream.

• updated dependencies and adapter.js
• changed fixed video width to maximum width limit

Selectable constraints + toggle 90° rotation on double click

The selected resolution is set each time you (re)start a source.
Double click on the video to rotate it 90 degrees and back.

• 1080p, 720p & 360p resolutions
• sourceId moved to button tooltip
• start window in 1280x720
• show gum errors in alerts
• adapter.js updated
• various styling improvements

electron-gum (electron v1.7.8)

downgrade electron to v1.7