Use flexible array for upvalues in closure.
Don't allow "super" outside of methods.
Start getting superclass constructors working.

This also means the metaclass inheritance hierarchy parallels
the regular inheritance chain so that the subclass can find
the superclass constructor.
More work on docs.
Make method_call benchmark use inheritance.

This also fixes a bug where constructors weren't being bound
correctly, and eliminates some unneeded instructions when
compiling ifs.

I also tweaked the other method_call languages to match Wren's.
Since Wren needs to do a super call to get to the parent _count,
the other languages do now too.

This is nice too because it means we're benchmarking super 
calls.
Add TODO about resolving ctors.
Use more conventional syntax for constructors.

They are now invoked like "new Foo".
Also, superclass constructors are now much less semantically
and syntactically weird. Since the instance is created before
any constructor is called, there's no point in time where the
instance isn't there.