ant: Add ant build logic for sphinx documentation
travis: Use ant to build documentation
travis: Install ant-contrib
travis: Install ant-optional
ant: Move taskdef to rules.xml
travis: Explicitly set CLASSPATH
ant: Add linkcheck targets
README: Document ant usage
Merge pull request #744 from rleigh-dundee/ant-build

Use ant to build sphinx docs
Removing 'only works for UNIX' comment from README
Merge pull request #747 from hflynn/readme-fix

Removing build commands 'only work for UNIX' from README