fix: add #!/usr/bin/env node header (#49)

Author: xudafeng

bin/detect-port.js

@@ -1,3 +1,5 @@
+#!/usr/bin/env node
+
 'use strict';
 
 const pkg = require('../package');

package.json

@@ -1,6 +1,6 @@
 {
   "name": "detect-port",
-  "version": "1.5.0",
+  "version": "1.5.1",
   "description": "Node.js implementation of port detector",
   "keywords": [
     "detect",