Fix broken link
Fix broken link

Currently links to https://facebook.github.io/draft-js/docs/docs/advanced-topics-block-components.html which has /docs/ repeated twice. =P
facebook/draft-js,SciMts/draft-js,dirkholsopple/draft-js,TripleDip/draft-js,brookslyrette/draft-js,brookslyrette/draft-js,tonygentilcore/draft-js,TripleDip/draft-js,SciMts/draft-js,davidchang/draft-js,tonygentilcore/draft-js,dirkholsopple/draft-js,davidchang/draft-js,johnmpotter/draft-js,johnmpotter/draft-js