Add rake "lint" target, fix errors

Add the rake "lint" target, and fix resulting minor errors, which were:

---
 manifests/mod/python.pp - WARNING: class not documented on line 1
 manifests/mod/wsgi.pp - WARNING: class not documented on line 1
 manifests/vhost.pp - WARNING: variable not enclosed in {} on line 80
 manifests/vhost.pp - WARNING: variable not enclosed in {} on line 82
 manifests/vhost/redirect.pp - WARNING: variable not enclosed in {} on line 43
 manifests/vhost/redirect.pp - WARNING: variable not enclosed in {} on line 45
---

Change-Id: I2213f314d4bf92b4ddf58dbb19a80783380a55ce