Default to --delay=5000 (5 seconds) for CI builds, where ensuring
rendering is complete is crucial and Travis instances may have high load.
Default to  --delay=1100 (1.1 seconds) for local builds, where there is
a greater chance that users are running the command in real-time.

The MANUBOT_ATHENAPDF_DELAY environment variable can now
be set to override default values.

For readability