Deprecate HTML4-error-reporting methods/classes and update pom.xml for the 1.5 release

[sideshowbarker]

This change deprecates all public methods related to reporting of HTML4-specific parse errors — as well as deprecating the entire nu.validator.htmlparser.common.DoctypeExpectation class, which is only used when reporting HTML4-specific parse errors. Compare to https://github.com/validator/htmlparser/commit/5c8fe7a

This change also updates the pom.xml file in preparation for the 1.5 release.