Move brief API documentation out of example
Move brief API documentation out of example

Really love this component and thought it might be helpful for other people if the props for a `<Draggable/>` were more clearly documented. I don't usually look in code examples for documentation about a given API and it might help people clearly see how to clearly use the module while still including an easy-to-get usage. Open to thoughts / feedback / &c.!
hemnstill/react-draggable,STRML/react-draggable,ericariyanto/react-draggable,LevInteractive/react-draggable,martinRoss/react-draggable,ericariyanto/react-draggable,LevInteractive/react-draggable,mcanthony/react-draggable,DelvarWorld/react-draggable,geminiyellow/react-draggable,mzabriskie/react-draggable,dkozar/react-draggable,Gitesoft/react-draggable,martinRoss/react-draggable,ericariyanto/react-draggable,hemnstill/react-draggable,DelvarWorld/react-draggable,martinRoss/react-draggable,dkozar/react-draggable,mzabriskie/react-draggable,dkozar/react-draggable,geminiyellow/react-draggable,mcanthony/react-draggable,LevInteractive/react-draggable,geminiyellow/react-draggable,DelvarWorld/react-draggable,emosbaugh/react-draggable,emosbaugh/react-draggable,mzabriskie/react-draggable,hemnstill/react-draggable,STRML/react-draggable,emosbaugh/react-draggable,hemnstill/react-draggable,mcanthony/react-draggable,STRML/react-draggable