Modularize try statement parsing

[abhijeetbhagat]

This Pull Request fixes/closes #375.

• Modularized the try statement parsing into separate modules as mentioned in the reply to the issue.
• Haven't implemented the entire catch parameter grammar parsing. Just kept the existing identifier parsing as it is for now.
• Added some tests for the try statement parsing.

[Razican]

Thanks for this contribution!
It seems that you need to re-base, since in #389 we added BindingIdentifier parsing. The change for this case was to parse the binding identifier like this:

// TODO: CatchParameter - BindingPattern
let catch_param = BindingIdentifier::new(self.allow_yield, self.allow_await)
    .parse(cursor)
    .map(Node::local)?;

This should just be used in the CatchParameter parser

[Razican]

This looks very good!
I think that CatchParameter should be in catch.rs, since it's directly related.

Check my other comments too, and see if they make sense.