fixes and tweaks for h2f test vectors

[kwantam]

This PR addresses the issue in #265 and also updates the data dumped out in the expand_message test vectors:

• adds len_in_bytes argument for each invocation
• removes security_param, which is an internal variable for sanity checking and not part of the API

Also, this PR updates printer.py to wrap correctly when the label is longer than 7 chars.

closes #265