call unlink function in unbind for v-if and v-partial (fix vuejs#728)

Author: yyx990803

src/directives/if.js

@@ -107,6 +107,11 @@ module.exports = {
     }
     this.unlink()
     this.unlink = null
+  },
+
+  // NOTE: this function is shared in v-partial
+  unbind: function () {
+    if (this.unlink) this.unlink()
   }
 
 }

src/directives/partial.js

@@ -9,6 +9,7 @@ module.exports = {
   // same logic reuse from v-if
   compile: vIf.compile,
   teardown: vIf.teardown,
+  unbind: vIf.unbind,
 
   bind: function () {
     var el = this.el