IE caches xhr responses pretty aggressively and after restoring the
previous response from cache, it blanks out the "Date" header (probably
by design). The solution for this test is to use a cache-busting query
parameter.

If the body passed to `xhr.send()` is `undefined`, the text sent would
literally be "undefined" on IE.

By default, all static files served from the test server were
"text/plain". IE auto-detects HTML and JavaScript content as such, but
refuses to display the style sheet until it is served as "text/css".

PhantomJS doesn't seem to send request body for PATCH:
https://github.com/ariya/phantomjs/issues/11384

Now only the whitelisted method names get normalized by uppercasing and
the rest are left untouched since HTTP method names in general are
case-sensitive.

In tests we must use `PATCH` (uppercase) because Node.js server doesn't
support `patch` (lowercase).

This fixes PUT/DELETE for IE 9 and PATCH for Node.js.

Auto-detect available port when running headless tests

By default the test server tried to run on port 3000, which would fail
with a misleading message if something else happened to occupy that port
on the system (such as a Rails app).

Now start incrementing the port number from 3900 and stop when the port
is found to be available.

Shell highlight

use shorthand npm installation

Add name/version/main so it can be installed from npm.

Add example of success and error handlers

I thought it would be nice to have an example of how to handle success and error handlers. It is not given how to implement this correctly. Maybe even my example is not the best way to do it, but wanted to contribute with a suggestion :-)

Test Server

Travis

Use of `Promise.reject` as a constructor

Ammended tets to also check error message, not just type.