Before, in browsers that had native `fetch` implementation the polyfill
code was never exercised by the test suite. This ensures that both
implementations are exercised.

If someone just cloned this project, they might be tempted to
`script/server` and try to run the test suite immediately. That won't
work, because they have to run `make` first to obtain all npm and bower
dependencies. However, they would get a blank HTML page which would be
confusing because it's not immediately apparent what they did wrong.

Now, an error message is rendered that suggests you should run `make`.

https://travis-ci.org/github/fetch/jobs/88862914

Allow making a POST request with an ArrayBuffer body

Run Sauce Labs CI for pull requests

[ci skip]

Closes #209, fixes #185

https://fetch.spec.whatwg.org/#dom-response-clone

Remove moot `version` property from bower.json

Every request now goes through general-purpose `saucelabs-api` command
which, by default, dumps the data in line-based format suitable for
parsing on the command line. If `--raw` is passed, raw JSON is returned
instead.

Disable Travis' own Sauce Labs integration

Use absolute URL in Response.redirect test

Avoids an issue where native implementations resolve and expand the URL.

Support Response.error() and Response.redirect()

Reject the Promise returned by fetch() when Request ctor throws

Fix incorrect assertion

Remove superfluous assignment

Closes #205.

Add webpack usage link.

Allow passing a Request instance to Request constructor

The fetch spec instructs that Request should throw a TypeError when
given a Request with an already consumed body, but Chrome's
implementation doesn't respect that yet.

This makes the test error more correct when the `then` block raises an
assertion error. The `catch` block needs to re-raise the same exception,
not swallow it and disguise it like another failure.

The new Request instance becomes essentially a clone of the old Request.
The original Request's body becomes unusable.

https://fetch.spec.whatwg.org/#dom-request