See comments - things are looking up.

Fixed bug in class visitor that happened when visited non-built-in
classes first.
Fixed the isSubType method, should be good now. I tested many possible
uses of this method and didn’t see any errors.
Changed one of the error messages in the parser because in wasn’t
entirely accurate.
Merge branch 'master' of https://github.com/scmorse/bantam

Conflicts:
	src/visitor/ClassVisitor.java