hx-include attribute

• The `this` modifier can be used in the hx-include selector9ms ‣

  this.server.respondWith('POST', '/include', function(xhr) {
    var params = getParameters(xhr)
    params.i1.should.equal('test')
    params.i2.should.equal('test')
    xhr.respond(200, {}, 'Clicked!')
  })
  make('<div id="i" hx-include="this"><input name="i1" value="test"/><input name="i2" value="test"/>' +
          '<button id="btn" hx-post="/include"></button></div>')
  var btn = byId('btn')
  btn.click()
  this.server.respond()
  btn.innerHTML.should.equal('Clicked!')