(FACT-346) Remove selinux_mode from schema

The selinux_mode fact was removed in 544260f, removing from the schema
also.
(FACT-349) Surface error messages when rescuing exceptions
Merge pull request #647 from adrienthebo/feature/facter-2/log-exceptions

(FACT-349) Surface error messages when rescuing exceptions
Merge branch 'facter-2'