Minor corrections to the texts (wording, typos etc.).

Shifted the diagrams to the left in the XML file, as xml2rfc was
complaining that some diagrams were too wide.
Additional minor editorial changes.

These are some of the changes suggested by Stephen in his email of
1 July 2014, 13:51 UTC.
Merge branch 'master' of https://github.com/DNSOP/dnssec-key-timing

Conflicts:
	draft-ietf-dnsop-dnssec-key-timing-04.xml