Fix UNKNOWN output for nagios_check >= 0.1.1

dbroeglin/nagios_check@24aab628b3df52eaa4da26eb30703f850c0b060b changed the
output of UNKNOWN errors to include the name of the exception class. Make
this optional for backwards compatibility.
Fix tests for store_message() output

Commit 9a3b411d4eb1af866f68529b303d2bb745f3e0a9 added a call to
`store_message` which changes the STDOUT to include a string that is
presented to humans, along with the machine parseable information that comes
after the pipe. Account for this in existing tests.
Setup Travis CI

Add metadata and default rake task for Travis CI. This will make future test
failures more apparent to contributors. Will need to be enabled in the
parent repo and any forks.
Merge pull request #5 from dcarley/tests

Fix tests and enable Travis CI