Allow ERB subclass to add token easily
While I want to use ERB in Rails, escape token "<%==" is not available in ERB and we can't add a new token to ERB easily.
To allow ERB subclass to add a new token easily, I splitted ERB::Compiler#compile to some small methods and created ERB::Compiler::Scanner#stags and ERB::Compiler::Scanner#etags.
With this patch, we'll be able to add a new stag or etag by overriding these methods.
sample.rb is a sample to create ERB subclass with "<%==" token.