Extended header parsing

What's Changed

• Comments around PCF CFST parsing/padding
• Updated examples including a browser decoding more headers
• Added XQH.get_header() method by @andrewkirillov-ibm in #4
• Updated to_string() to strip NULLs by @andrewkirillov-ibm in #11

New Contributors

• @andrewkirillov-ibm made their first contribution in #4

Full Changelog: 2.0.0...2.0.1