Auto-generate a secret key for development mode.

xppl/config.py

@@ -1,5 +1,6 @@
 """The Application settings."""
 
+from os import environ, urandom
 from os.path import abspath, dirname, isdir, join
 
 
@@ -30,3 +31,7 @@ class Development(Base):
     DEBUG = True
     TESTING = True
     DOMAIN = 'http://localhost'
+    SECRET_KEY = environ.get(
+        'XPPL_SECRET_KEY',
+        urandom(24).hex()
+    )