Add base in abstract mode (fix #983) (#1045)

* Add base in abstract mode

* Abtract mode give base in 2nd argument

Author: atinux

src/history/abstract.js

@@ -7,8 +7,8 @@ export class AbstractHistory extends History {
   index: number;
   stack: Array<Route>;
 
-  constructor (router: VueRouter) {
-    super(router)
+  constructor (router: VueRouter, base: ?string) {
+    super(router, base)
     this.stack = []
     this.index = -1
   }

src/index.js

@@ -48,7 +48,7 @@ export default class VueRouter {
         this.history = new HashHistory(this, options.base, this.fallback)
         break
       case 'abstract':
-        this.history = new AbstractHistory(this)
+        this.history = new AbstractHistory(this, options.base)
         break
       default:
         process.env.NODE_ENV !== 'production' && assert(false, `invalid mode: ${mode}`)