Start working on a Ruby bridge

Example:

```ruby
$LOAD_PATH << 'lib'
require 'duktape'

ctx = Duktape::Context.new(ruby_bridge: true)

ctx.exec_string(<<-JS, __FILE__)
Ruby.decorate = function(obj) {
  return new Proxy(obj, {
    get: function(target, key) {
      if (key == 'toString')
        key = 'to_s';

      return function() {
        var res = Ruby.send(target, key, arguments);
        if (Ruby.isObject(res)) {
          return Ruby.decorate(res);
        } else {
          return res;
        }
      }
    }
  });
}

var main = Ruby.decorate(Ruby.main)
var DB = main.eval("require 'sequel'; Sequel.sqlite")
print(DB.execute('select 1 + 1').to_a())
JS
```

@josh: Not sure if you need this, but it was cool playing with it.