Bump future from 0.16.0 to 0.17.0

Bumps [future](https://github.com/PythonCharmers/python-future) from 0.16.0 to 0.17.0.
- [Release notes](https://github.com/PythonCharmers/python-future/releases)
- [Changelog](https://github.com/PythonCharmers/python-future/blob/master/docs/changelog.rst)
- [Commits](PythonCharmers/python-future@v0.16.0...v0.17.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements/base.txt

@@ -18,7 +18,7 @@ requests==2.20.0
 static==1.1.1
 whitenoise[brotli]==4.1
 urllib3[secure]==1.24
-future==0.16.0
+future==0.17.0
 coreapi==2.3.3
 Markdown==3.0.1
 pygments==2.2.0