tox: bring back test for letshelp_letsencrypt

tox.ini

@@ -21,6 +21,8 @@ commands =
     nosetests -v letsencrypt_apache
     pip install -e letsencrypt-nginx
     nosetests -v letsencrypt_nginx
+    pip install -e letshelp-letsencrypt
+    nosetests -v letshelp_letsencrypt
 
 setenv =
     PYTHONPATH = {toxinidir}