Fix missing semicolon.
Treat methods and static methods separately in checking for duplicates.
Require that constructors be regular methods.
Check for methods named 'prototype'.
Limit 'constructor' getter/setter checks to class definitions.
Comments: reformat and add some more relevant quotes from the ES6 spec.
Fix indentation.
Fix error message calls.
Add test for checks of class and method naming.

There is some overlap with reserved var checking, so I'm not sure how
useful the 'eval' and 'arguments' checks are.