upgrade to unified uritemplate 3.0.0 [closes #57]

[simon-weber]

As of uritemplate 3.0.0 and uritemplate.py 3.0.2, the two packages are equivalent.
There were no changes to functionality; see
https://github.com/sigmavirus24/uritemplate/blob/master/HISTORY.rst.

This resolves the conflict described in #57.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[simon-weber]

I signed it!

[googlebot]

CLAs look good, thanks!

[theacodes]

Thanks, @simon-weber!

[simon-weber]

Sure thing. Any idea when this will be released? I'm eager to get rid of the special cases we had for resolving this 😁

[theacodes]

Whenever I get the time to cut another release. Maybe sometime next week?

[simon-weber]

Sounds good; thanks.