Fix w3c validator issues.
Fix w3c validator issues.
Fix w3c validator issues.
Fix w3c validator issues.
Fix w3c validator issues.
Merge pwo/buildbot:w3c-validator (PR #1080)

+autopep8
Docs: add an 'import' in one spot to make the recipe easier to swallow
Merge pull request #1081 from jaredgrubb/doc-props-add-import

Docs: add an 'import' in one spot to make the recipe easier to swallow
fix pngstatus if the build is currently in progress
png status by revision hash
Merge kviktor/buildbot:png-status-building (PR #1082)
fix pngstatus test
update docs for statuspng
return deferreds from addLog, addCompleteLog, and log.add*
return deferreds from addHTMLLog and addURL
cmd.add* return deferreds
backport ShellMixin and CommandMixin from nine
add step.setStateStrings
add docs for setStateStrings
add step.*Statistic methods for new-style steps