fix(core): dont import full RxJS library

Closes #619

Author: sebholstein

src/core/directives/google-map-polyline.ts

@@ -1,5 +1,5 @@
 import {AfterContentInit, ContentChildren, Directive, EventEmitter, OnChanges, OnDestroy, QueryList, SimpleChanges} from '@angular/core';
-import {Subscription} from 'rxjs/Rx';
+import {Subscription} from 'rxjs/Subscription';
 
 import {PolyMouseEvent} from '../services/google-maps-types';
 import {PolylineManager} from '../services/managers/polyline-manager';

src/core/services/managers/polyline-manager.ts

@@ -1,5 +1,6 @@
 import {Injectable, NgZone} from '@angular/core';
-import {Observable, Observer} from 'rxjs/Rx';
+import {Observable} from 'rxjs/Observable';
+import {Observer} from 'rxjs/Observer';
 
 import {SebmGoogleMapPolyline} from '../../directives/google-map-polyline';
 import {SebmGoogleMapPolylinePoint} from '../../directives/google-map-polyline-point';