Fix burn_after_reading feature, along with zerobin.py

zerobin.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 # coding: utf-8
 
-from zerobin.routes import main
+from zerobin.cmd import main
 
 main()

zerobin/paste.py

@@ -172,7 +172,6 @@ class Paste(object):
         # deleting the paste
         if "burn_after_reading" == self.expiration:
             expiration = self.expiration + '#%s' % datetime.now()  # TODO: use UTC dates
-            expiration = self.expiration
         else:
             expiration = as_unicode(self.expiration)