docs(expand): add inline docs for expand
docs(expand): add inline docs for expand

RxJS-CN/RxJS-Docs-CN,RxJS-CN/RxJS-Docs-CN,ReactiveX/RxJS,staltz/RxJSNext,elliotschi/rxjs,robwormald/RxJS,adrianomelo/RxJSNext,jinroh/RxJS,jayphelps/rxjs,ReactiveX/rxjs,RxJS-CN/RxJS-Docs-CN,Brocco/RxJS,elliotschi/rxjs,adrianomelo/RxJSNext,jayphelps/rxjs,jinroh/RxJS,adrianomelo/RxJS-1,gluck/RxJS,robwormald/RxJS,ReactiveX/rxjs,jinroh/RxJS,adrianomelo/RxJS-1,ReactiveX/rxjs,elliotschi/rxjs,gluck/RxJS,gluck/RxJS,Brocco/RxJS,saneyuki/RxJS,martinsik/rxjs,benlesh/RxJS,SangKa/RxJS-Docs-CN,Igorbek/rxjs5,kwonoj/RxJS,jadbox/RxJS,benlesh/RxJS,jadbox/RxJS,trxcllnt/RxJS,Brocco/RxJS,benlesh/RxJS,figueredo/RxJS,SangKa/RxJS-Docs-CN,jayphelps/rxjs,figueredo/RxJS,kwonoj/RxJS,jinroh/RxJS,martinsik/rxjs,kwonoj/RxJS,saneyuki/RxJS,trxcllnt/RxJS,adrianomelo/RxJSNext,SangKa/RxJS-Docs-CN,Igorbek/rxjs5,robwormald/RxJS,jayphelps/rxjs,figueredo/RxJS,adrianomelo/RxJSNext,adrianomelo/RxJS-1,ReactiveX/RxJS,Brocco/RxJS,staltz/RxJSNext,martinsik/rxjs,robwormald/RxJS,gluck/RxJS,IgorMinar/RxJS,Igorbek/rxjs5,trxcllnt/RxJS,jadbox/RxJS,IgorMinar/RxJS,Igorbek/rxjs5,staltz/RxJSNext,jayphelps/rxjs,SangKa/RxJS-Docs-CN,ReactiveX/RxJS,kwonoj/RxJS,benlesh/RxJS,jadbox/RxJS,elliotschi/rxjs,martinsik/rxjs,staltz/RxJSNext,ReactiveX/rxjs,adrianomelo/RxJS-1,ReactiveX/RxJS,trxcllnt/RxJS,RxJS-CN/RxJS-Docs-CN,figueredo/RxJS