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.

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.

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.

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