allow posts to specify "updated" field
if this field is present, last updated time will be added to the meta section
fix wrong date that will change automatically when built
use a static one hard-coded in the front matter
remove redundant liquid date formatting
as it's hardcoded anyway, case #1
move setup jekyll post to "articles" category
case #1
update selenium on travis ci post
case #1
Merge branch 'feature/#1'