Allow match to be used as a Statement

The `match` operator macro in most pattern-matching languages can be used as a statement. Currently, Sparkler returns an anonymous function expression, which is not a valid statement but can be used as one if simply wrapped in parentheses.

This lets us have syntax like so:

```rust
var num = 1;
match num {
  0 => alert("zero"),
  1 => alert("one"),
  _ => alert("something else")
}
```

Which will become more useful since I'm working on adding more [Rust-like features](http://static.rust-lang.org/doc/master/tutorial.html#pattern-matching) like multiple patterns via pipe `0 | 1` and ranges `0..10`.