Core htmx API test

• ajax api works with Hx-Select overrides select8ms ‣

  this.server.respondWith('GET', '/test', [200, { 'HX-Reselect': '#d2' }, "<div id='d1'>foo</div><div id='d2'>bar</div>"])
  var div = make("<div id='target'></div>")
  htmx.ajax('GET', '/test', { target: '#target', select: '#d1' })
  this.server.respond()
  div.innerHTML.should.equal('<div id="d2">bar</div>')