Upgrade to PHP 7.1
Summary:
As the notifications center now uses PHP 7.1,
we so switch to the relevant PHP 7 base image.
Fixes composer issue as it tries to validate dependencies
requirements for dev, even when --no-dev is passed.
Ref T1062.
Test Plan:
Rebuild the container: docker build -t nasqueron/notifications .
Run tests.
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T1062
Differential Revision: https://devcentral.nasqueron.org/D782