Use anonymous class in test

Make more consistent with test suite.
Remove unused method
Sequence blank slugs without separator

Filter out unwanted slug candidates from generator.
Merge pull request #571 from xymbol/fix-blank-slugs

Fix blank slugs
Update gem dependencies
Update minitest names

Make sure it conforms to most recent gem version.
Merge pull request #579 from xymbol/fix-travis-ci

Update minitest names
Add missing tests

Improve coverage for candidates.
Merge pull request #578 from xymbol/candidates-tests

Add missing tests
Fix missed minitest name

Mea culpa, as previous changes overlapped over time.
Remove anonymous test for Marshal as we don't use anonymous classes anymore.
Merge pull request #581 from norman/remove-anonymous-test

Remove anonymous test for Marshal as we don't use anonymous classes anymore