changed unrar method to use unrar rather than library

this is because it became aparent that this is quite annoying to setup in linux and windows.
also included the rarfile library to save on confusion.

comic/models.py

@@ -1,7 +1,7 @@
 from django.db import models
 from django.utils.http import urlsafe_base64_encode, urlsafe_base64_decode
 
-from unrar import rarfile
+from comic import rarfile
 import zipfile
 from os import path
 import os