add crc64 demo

Author: carsonxu

demo/crc64.js

@@ -0,0 +1,9 @@
+var crc64 = require("crc64-ecma182.js");
+var path = require('path');
+
+var hash = crc64.crc64(Buffer.from("hello!"));
+console.log('string crc64:', hash);
+
+crc64.crc64File(path.join(__dirname, "./demo.js"), function(err, hash) {
+    console.log('file crc64:', err || hash);
+});

package.json

@@ -38,6 +38,7 @@
   },
   "devDependencies": {
     "batch": "^0.6.1",
+    "crc64-ecma182.js": "^1.0.0",
     "mocha": "^4.0.1",
     "nyc": "^15.1.0",
     "qcloud-cos-sts": "^3.0.0"