Update to voxel-engine 0.20.1
Update demo to support voxel-player with (game,opts) constructor
Revert "Update demo to support voxel-player with (game,opts) constructor"

This reverts commit 4dcb6e1700158f5aa0be683c70c210a2fd73bb6a.
Update to voxel-engine 0.20.1; tighten dev dependencies

Conflicts:
	package.json
Fix constructor without options (game only) (as in demo)
Use my branch of voxel-engine, for testing experimental useAtlas toggle