added sudo
fixed bugs & outputs
Integrated linkcheck to Travis, ubuntu.md & broken link fixes

- travis configs
- fixed broken links
- added ubuntu.md
Test locally hosted docs rather than deepdive.stanford.edu
Added jekyll installation on Travis
sleep 3 after make serve on Travis
Handles timeout when doing linkcheck
Merge pull request #128 from HazyResearch/zifei-linkchecker

Integrated linkchecker into Travis Test