Add support for `this` and `arguments`

I have not tested sourcemaps - I don't know how exactly they work.
Re-add support for non-identifier lvars.
Merge branch 'master' of https://github.com/BYVoid/continuation
Re-add variable declaration in the outer scope

I realize now why that was there. It allows you to refer to the
variables *before* the `cont` call. I figure that's so `cont` variables
are similar to ordinary variables:

    console.log(x); // undefined, but not an error!
    async(stuff, cont(err, x));

if x was a normal variable:

    console.log(x); // undefined, but not an error!
    var x = 42;
Replace all parameters with temporary variables.
Bump version to 0.1.4.

Add unit test for this and argument.
Update dependencies.