Use different print-servlet in examples.
Merge pull request #222 from marcjansen/printurl

Use different print-servlet in examples.
Only allow submission when form is valid.

If the `comment` field is empty, the print-servlet complains with a
nasty and long textual error message.
Fix the README part about headless testing

After we merge #220, the script can be called from mostly anywhere, currently only from the root of the repository.
Merge pull request #223 from marcjansen/printform-example

This is a simple and nice fix. Tested and approved to be working fine.
Will merge this one...