chore(package): update acorn-es7-plugin to 1.0.10 and stop pinning of acorn version

refs: #20 (comment)

Author: twada

package.json

@@ -17,8 +17,8 @@
     }
   ],
   "dependencies": {
-    "acorn": ">=2.5.2 <2.6.0",
-    "acorn-es7-plugin": "^1.0.9",
+    "acorn": "^2.5.2",
+    "acorn-es7-plugin": "^1.0.10",
     "array-foreach": "^1.0.1",
     "array-map": "0.0.0",
     "array-reduce": "0.0.0",