Add working DNS test.
Ignore htmlcov directory.
Simplify DNSValidator return statement.
Remove extraneous test code.
Clean up tests.
Add coverage configuration file.
Add BaseDiagnosis test.
DRY up validator tests.
Make sure EmailValidator.is_email raises NotImplementedError.
Increase Reference coverage.
Replace SystemExits with InvalidErrors.
Clean up and PEP-8ify ParserValidator.
Clean up and PEP-8ify test files.