hx-headers attribute

• basic hx-headers javascript: works8ms ‣

  this.server.respondWith('POST', '/vars', function(xhr) {
    xhr.requestHeaders.i1.should.equal('test')
    xhr.respond(200, {}, 'Clicked!')
  })
  var div = make('<div hx-post="/vars" hx-headers="javascript:i1:\'test\'"></div>')
  div.click()
  this.server.respond()
  div.innerHTML.should.equal('Clicked!')