update vexflow to new version 1.2.85 (#315)

fixes delayed ornaments, grace notes, notesubgroup re-render x-shift in Vexflow

package.json

@@ -53,7 +53,7 @@
     "loglevel": "^1.5.0",
     "shortid": "^2.2.6",
     "typescript-collections": "^1.1.2",
-    "vexflow": "^1.2.84"
+    "vexflow": "^1.2.85"
   },
   "devDependencies": {
     "@types/chai": "^4.0.3",