keep command docs in README.md, not CONTRIBUTING.md
keep command docs in README.md, not CONTRIBUTING.md

aframevr/aframe,RSpace/aframe,jzitelli/aframe,ngokevin/aframe,mkungla/aframe,googlecreativelab/aframe,fernandojsg/aframe,weddingdj/aframe,googlecreativelab/aframe,chenzlabs/aframe,darkwing/aframe,dmarcos/aframe,jaxmolina/ar,jaxmolina/ar,darkwing/aframe,MatthewShotton/aframe,aframevr/aframe-core,wizgrav/aframe,MatthewShotton/aframe,msimpson/aframe,msimpson/aframe,ngokevin/aframe,jzitelli/aframe,weddingdj/aframe,dmarcos/aframe,aframevr/aframe-core,chenzlabs/aframe,aframevr/aframe,fernandojsg/aframe,mkungla/aframe,wizgrav/aframe,RSpace/aframe