Core htmx API test

• ajax api does not fall back to body when target invalid2ms ‣

  this.server.respondWith('GET', '/test', 'foo!')
  var div = make("<div id='d1'></div>")
  htmx.ajax('GET', '/test', '#d2')
  this.server.respond()
  document.body.innerHTML.should.not.equal('foo!')