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](https://github.com/pallets/flask/compare/0.12.2...1.0)

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/requirements.txt b/requirements.txt
index eb7cefe..566c1f3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,7 +15,7 @@
 elasticsearch==5.4.0
 elasticsearch-dsl==5.3.0
 enum34==1.1.6
-Flask==0.12.2
+Flask==1.0
 flower==0.9.2
 futures==3.1.1
 idna==2.5