Bump owslib from 0.11.0 to 0.28.1

Bumps [owslib](https://github.com/geopython/OWSLib) from 0.11.0 to 0.28.1.
- [Release notes](https://github.com/geopython/OWSLib/releases)
- [Changelog](https://github.com/geopython/OWSLib/blob/master/CHANGES.rst)
- [Commits](geopython/OWSLib@0.11.0...0.28.1)

---
updated-dependencies:
- dependency-name: owslib
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,6 +1,6 @@
 Django==1.8.7
 MultipartPostHandler==0.1.0
-OWSLib==0.11.0
+OWSLib==0.28.1
 Paver==1.2.1
 Unidecode==0.4.19
 amqp==1.4.9