This shouldn't have been public
VisitorBridge doesn't care what the exception type is
SourceCode only really needed to be an interface
Added an initialize method to SourceCode.Builder

DelegatSourceCode is now more consistent with the rest of the
SourceCodes (it's Builder restricted
Instead of forcing all NestedClass<?> and MethodDeclaration instances of
SourceCode to be static, I moved that decision to the *Definer class.
Started testing MethodDefiner. Fixed an issue in MethodSourceCode where
toCanonicalString wasn't being called where it should have been.