Avoid hardcoding full paths for Jekyll and Sphinx.
The `/usr/local/bin/` softlink isn't necessary.
Fail fast in site.yml.
Use mon_email and mon_pagerduty.
mon_pagerduty is undefined, not false.
Merge pull request #750 from rackerlabs/full-jekyll-path

Avoid hardcoding full paths for Jekyll and Sphinx.
Merge pull request #798 from rackerlabs/fail-without-explicit-monitoring

Fail fast without an explicit monitoring setup.