fix(html5): initial path in HTML5 vs base (vuejs#3555)

Author: eyedean

src/history/html5.js

@@ -87,7 +87,9 @@ export class HTML5History extends History {
 
 export function getLocation (base: string): string {
   let path = window.location.pathname
-  if (base && path.toLowerCase().indexOf(base.toLowerCase()) === 0) {
+  // base="/a" shouldn't turn path="/app" into "/a/pp" https://github.com/vuejs/vue-router/issues/3555
+  if (base && ((path.toLowerCase() === base.toLowerCase()) 
+	  || (path.toLowerCase().indexOf(cleanPath(base.toLowerCase() + "/")) === 0))) {
     path = path.slice(base.length)
   }
   return (path || '/') + window.location.search + window.location.hash