[WIP][Travis] Setup PHP7 testing on travis, bump requriment to PHP 5.5

Notes:
- Minimum version for use with eZ Platform is PHP 5.6
- This will most likly fail becasue of PHPUnit version, so might need some help on that part to get this to pass

.travis.yml

@@ -1,38 +1,35 @@
 language: php
 
-php:
-  - 5.3
-  - 5.3
-  - 5.4
-  - 5.5
-  - 5.6
+services:
+  - mysql
+  - postgresql
+
+cache:
+  directories:
+    - $HOME/.composer/cache/files
 
 branches:
   only:
     - master
-#    - 5.4
-#    - stable-5.3
 
 env:
   global:
     - DB_NAME="testdb"
-  matrix:
-    - DB="mysql" DB_USER="root"
-    - DB="postgresql" DB_USER="postgres"
 
 # Aim to run tests on all versions of php, make sure each db is run at least once
 matrix:
-  exclude:
-    - php: 5.3.3
+  include:
+    - php: 5.5
       env: DB="postgresql" DB_USER="postgres"
-    - php: 5.3
+    - php: 5.6
       env: DB="mysql" DB_USER="root"
-    - php: 5.4
+    - php: 7.0
       env: DB="postgresql" DB_USER="postgres"
-    - php: 5.5
+    - php: 7.1
       env: DB="mysql" DB_USER="root"
-    - php: 5.6
-      env: DB="postgresql" DB_USER="postgres"
+# Will need to update phpunit for this: https://travis-ci.org/ezsystems/ezpublish-legacy/jobs/279543965#L625
+#    - php: 7.2
+#      env: DB="postgresql" DB_USER="postgres"
 
 before_script:
   - if [ $DB == "mysql" ]; then mysql -e "CREATE DATABASE IF NOT EXISTS $DB_NAME;" -u$DB_USER ; fi

composer.json

@@ -17,7 +17,7 @@
         "ezsystems/eztags-ls": "eztags is a full tagging/taxonomy solution for eZ Publish replacing the simpler builtin ezkeywords datatype"
     },
     "require": {
-        "php": ">=5.3.3",
+        "php": "~5.5|~7.0",
         "ext-dom": "*",
         "ext-libxml": "*",
         "ext-mbstring": "*",