minor symfony#15678 [travis] Add PHP 7 to allowed failures until segfaults are fixed (nicolas-grekas)

This PR was merged into the 2.3 branch.

Discussion
----------

[travis] Add PHP 7 to allowed failures until segfaults are fixed

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

57232ef [travis] Add PHP 7 to allowed failures until segfaults are fixed

Author: fabpot

.travis.yml

@@ -14,9 +14,12 @@ matrix:
         - php: 5.4
         - php: 5.5
         - php: 5.6
-          env: deps=low
-        - php: 7.0
           env: deps=high
+        - php: 7
+        - php: 5.6
+          env: deps=low
+    allow_failures:
+        - php: 7
     fast_finish: true
 
 services: mongodb