fix(transformer): Corrected typo of transform method

Author: prog110

src/interceptor-service.ts

@@ -186,7 +186,7 @@ export class InterceptorService extends Http {
 
         let response$ = super.request(transformedRequest.url, transformedRequest.options);
         if (this._realResponseObservableTransformer) {
-          response$ = this._realResponseObservableTransformer.tranform(response$, transformedRequest, new this.HttpDirect(), this);
+          response$ = this._realResponseObservableTransformer.transform(response$, transformedRequest, new this.HttpDirect(), this);
         }
 
         return response$.map((response: Response) => {

src/real-response-observable-transformer.ts

@@ -14,7 +14,7 @@ import { InterceptorService } from './interceptor-service';
  * 2. Allows user to retry the request if the requets is expired due to connection timeout using `Observable.retry`/`Observable.retryWhen`
  */
 export interface RealResponseObservableTransformer {
-  tranform(response$: Observable<Response>,
+  transform(response$: Observable<Response>,
     request: InterceptorRequest,
     http: HttpDirect,
     interceptorService: InterceptorService): Observable<Response>;