[TASK] Travis-ci: Add PHP 7 nightly

Add PHP to monitor the situation and fix issues
as soon as the environment stabilized.

Change-Id: Ic08a6464c6be1fe43bc98a62d2bdca1acd6c814f
Releases: master
Reviewed-on: http://review.typo3.org/37248


Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>

.travis.yml

@@ -2,12 +2,15 @@ language: php
 
 matrix:
   allow_failures:
+    - php: 7
     - php: hhvm-nightly
   include:
     - php: 5.5
       env: UNIT_TESTS=yes FUNCTIONAL_TESTS=yes PHP_LINT=yes XLF_CHECK=yes
     - php: 5.6
       env: UNIT_TESTS=yes FUNCTIONAL_TESTS=yes PHP_LINT=yes
+    - php: 7
+      env: UNIT_TESTS=yes
     - php: hhvm-nightly
       env: UNIT_TESTS=yes