altered username to lower case because of authorization troubles

Logins failed because Email is handled case sensitiveley by Mastodon obviously. Added s.lower() to fix this.

mastobot.py

@@ -42,11 +42,11 @@ for account in transitions:
     # Connect with Mastodon-Account
     try:
         usercreds = mastodon.log_in(
-            account['masto_username'],
+            account['masto_username'].lower(),
             account['masto_passwd']
         )
     except:
-        print(account['masto_username'])
+        print(account['masto_username'].lower())
         print("Login failed!")
         continue