As a user of Brown Dog Box Client I want the server to cache tokens so I'm not generating new tokens on every skills invocation.

Acceptance Criteria:

1. Set token timeout value in config file to be 10 seconds
2. Submit a skills invocation and see that a new token is requested
3. Submit a second invocation within 10 seconds and see that the token is reused
4. Wait for 10 seconds and send a thrid invocation and see that the token is expired and a new one is requested