fix case bug, and filename in start command

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "lint": "eslint src test",
     "pretest": "npm run lint",
-    "start": "node bin/io-bot.js",
+    "start": "node bin/io-bot",
     "demo": "node example/ding-dong-bot.js",
     "test": "cross-env TAP_TIMEOUT=600 tap --reporter=tap test/{*,**/*}.spec.js"
   },

src/puppet-web/browser.js

@@ -26,7 +26,7 @@ class Browser extends EventEmitter {
   } = {}) {
     super()
     log.verbose('PuppetWebBrowser', 'constructor()')
-    this.head = head || false
+    this.head = String(head).toLowerCase() || false
     this.sessionFile = sessionFile // a file to save session cookies
 
     this.live = false