Fix bug in parsing of concise method names

I started by doing a little house keeping around unit test organization. The bug fix itself is in the second commit:

> When the ES6 concise method syntax is used to declare a method, no new
> entry is created in the local environment record. Because of this, the
> method name should *not* be interpreted as a local variable, and
> declaring a variable of that name should raise no warnings.
>
> Resolves gh-2022