introduce Validator#init to simplify validator instantiation
migrate Validator abstract
making implementation of init method optional
remove ClassUtils
 it is used only from RedPen.
introduce package private "preInit" method
now Validator holds ValidatorConfiguration and SymbolTable. They're accessible via getter methods.
Merge branch 'master' of https://github.com/recruit-tech/redpen into validator-init
Tiny fix
Merge pull request #240 from recruit-tech/validator-init

make validator abstract