Merge pull request #27 from ndw/xproc20

Added more links to the top-level repo README
Serialize as xhtml so that we don't get weird HTML artifacts
Merge pull request #63 from ndw/xproc20

Serialize as xhtml so that we don't get weird HTML artifacts
Added new secure vars
First stab at removing XPath 1.0
Merge branch 'remove-xpath-10' of github.com:ndw/specification into remove-xpath-10