chore(): Fix for Travis master and adding a CI/CD pipeline

package.json

@@ -83,7 +83,7 @@
     "systemjs": "^0.19.16",
     "systemjs-builder": "^0.15.7",
     "traceur": "0.0.96",
-    "typescript": ">=2.7.2 <2.8.0, >=3.1.1 <3.2"
+    "typescript": "^3.1.6"
   },
   "typings": "index.d.ts"
 }

src/database/list/audit-trail.ts

@@ -9,7 +9,7 @@ import { skipWhile, withLatestFrom, map, scan } from 'rxjs/operators';
 export function auditTrail<T>(query: DatabaseQuery, events?: ChildEvent[]): Observable<SnapshotAction<T>[]> {
   const auditTrail$ = stateChanges<T>(query, events)
     .pipe(
-      scan<SnapshotAction<T>>((current, action) => [...current, action], [])
+      scan((current, action) => [...current, action], [])
     );
   return waitForLoaded<T>(query, auditTrail$);
 }