Bump flask from 0.12.2 to 1.0

Bumps [flask](https://github.com/pallets/flask) from 0.12.2 to 1.0.
- [Release notes](https://github.com/pallets/flask/releases)
- [Changelog](https://github.com/pallets/flask/blob/master/CHANGES.rst)
- [Commits](pallets/flask@0.12.2...1.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ certifi==2017.7.27.1
 chardet==3.0.4
 click==6.7
 docutils==0.14
-Flask==0.12.2
+Flask==1.0
 Flask-Sphinx-Themes==1.0.1
 idna==2.6
 imagesize==0.7.1