hx-include attribute

• `inherit` can be used to expand parent hx-include9ms ‣

  this.server.respondWith('POST', '/include', function(xhr) {
    var params = getParameters(xhr)
    params.i1.should.equal('test1')
    params.i2.should.equal('test2')
    xhr.respond(200, {}, 'Clicked!')
  })
  make('<div hx-include="#i1">' +
    '   <button id="btn" hx-include="inherit, #i2" hx-post="/include"></button>' +
    '</div>' +
    '<input id="i1" name="i1" value="test1"/>' +
    '<input id="i2" name="i2" value="test2"/>')
  var btn = byId('btn')
  btn.click()
  this.server.respond()
  btn.innerHTML.should.equal('Clicked!')