* Improve robustness of the GAstVisitor dispatching by runtime error throwing   If none of the alternatives match.
* Improve robustness of the GAstVisitor dispatching by runtime error throwing
  If none of the alternatives match.

* Fixes #136 - Rule production note visited.

* Removes type assertion in the Visitor Dispatching as the modern typescript compiler can infer
  those due to the instanceof operator and thus provide better type checking.

relates to #135

SAP/chevrotain,SAP/chevrotain,SAP/chevrotain,SAP/chevrotain