chore(package.json): pin dev dependency package to known good
chore(package.json): pin dev dependency package to known good

closes #550

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