[minor] Clean up path.join

Author: 3rd-Eden

install.js

@@ -6,8 +6,8 @@
 var fs = require('fs')
   , path = require('path')
   , spawn = require('cross-spawn')
-  , hook = path.join(__dirname, './hook')
-  , root = path.resolve(__dirname, '../..')
+  , hook = path.join(__dirname, 'hook')
+  , root = path.resolve(__dirname, '..', '..')
   , exists = fs.existsSync || path.existsSync;
 
 //