Implemented requested changes

* Made docker images specific
* Added STORAGE_DRIVER question to rancher-compose

In addition:

* Updated README with important usage note concerning email confirmation

templates/huginn/0/rancher-compose.yml

@@ -31,7 +31,7 @@ catalog:
         description: Require newly registered users to confirm their Email address
         label: Require Confirmed Email
         required: true
-        default: true
+        default: false
         type: boolean
       - variable: SMTP_USER_NAME
         label: SMTP Username
@@ -71,6 +71,12 @@ catalog:
         label: Additional Gems
         required: false
         type: string
+      - variable: STORAGE_DRIVER
+        description: Rancher storage driver to use for database volume
+        label: Storage Driver
+        default: local
+        required: true
+        type: string
 services:
   postgres:
     scale: 1