Remove || which causes `set -e` not to work

I believe this is the issue causing #97.

Short story: `set -e` is complicated (http://mywiki.wooledge.org/BashFAQ/105, http://fvue.nl/wiki/Bash:_Error_handling)

Long story: When you make a command the first part of an `||` it turns off the normal `set -e` behavior for that command. What was happening specifically for `check_documentation_coverage` was that the first YARD command would fail, but the second would still run and succeed, and so the captured exit code stored as `$result` was still 0.

:santa: