upgrade most-subject

Author: jcouyang

lib/engine/most.es6

@@ -1,5 +1,5 @@
 import {from,mergeArray} from 'most'
-import {subject} from 'most-subject'
+import {async as subject} from 'most-subject'
 export default function Engine() {
   const intentStream = subject(),
         historyStream = subject(),

package.json

@@ -25,7 +25,7 @@
   },
   "dependencies": {
     "most": "^1.0.5",
-    "most-subject": "^4.1.3",
+    "most-subject": "^5.2.0",
     "react": "^15.3.2",
     "rx": "^4.1.0"
   },