fix updates warning about older versions

lib/check-update.js

@@ -2,6 +2,7 @@ import ms from 'ms';
 import pkg from '../../package'; // relative to `build/` :\
 import fetch from 'node-fetch';
 import chalk from 'chalk';
+import compare from 'semver-compare';
 
 const isTTY = process.stdout.isTTY;
 

package.json

@@ -69,6 +69,7 @@
     "node-fetch": "1.5.3",
     "progress": "1.1.8",
     "resumer": "0.0.0",
+    "semver-compare": "1.0.0",
     "socket.io-client": "1.4.6",
     "spdy": "3.3.3",
     "split-array": "1.0.1",