Merge pull request #21 from reschke/master

update HTML5 reference
respond to Ned Freed first set of comments

https://www.ietf.org/mail-archive/web/apps-discuss/current/msg13370.html
respond to t.petch comments

https://www.ietf.org/mail-archive/web/apps-discuss/current/msg13373.html
https://www.ietf.org/mail-archive/web/apps-discuss/current/msg13419.html
minor rewrites

strings of characters are always 'encoded'. Remove a 'generally' where
it didn't apply.
bump version
add additional security paragraph
move Section 1 into a note, add metadata, avoid TABs in artwork