Drop PHP 5.6 support, test latest 4.3 release

Author: wilr

.travis.yml

@@ -8,14 +8,14 @@ env:
 
 matrix:
   include:
-    - php: 5.6
-      env: DB=MYSQL INSTALLER_VERSION=4.2.1 PHPCS_TEST=1 PHPUNIT_TEST=1
-    - php: 7.0
-      env: DB=PGSQL INSTALLER_VERSION=4.2.1 PHPUNIT_TEST=1
-    - php: 7.0
-      env: DB=MYSQL INSTALLER_VERSION=4.2.1 PHPUNIT_TEST=1
     - php: 7.1
-      env: DB=MYSQL INSTALLER_VERSION=4.2.1 PHPUNIT_COVERAGE_TEST=1
+      env: DB=MYSQL INSTALLER_VERSION=4.3.3 PHPCS_TEST=1 PHPUNIT_TEST=1
+    - php: 7.2
+      env: DB=PGSQL INSTALLER_VERSION=4.3.3 PHPUNIT_TEST=1
+    - php: 7.2
+      env: DB=MYSQL INSTALLER_VERSION=4.3.3 PHPUNIT_TEST=1
+    - php: 7.2
+      env: DB=MYSQL INSTALLER_VERSION=4.3.3 PHPUNIT_COVERAGE_TEST=1
 
 before_script:
  # Init PHP

composer.json

@@ -21,7 +21,6 @@
     }
   ],
   "require": {
-    "php": ">=5.6.0",
     "silverstripe/cms": "^4",
     "silverstripe/asset-admin": "*",
     "silverstripe/silverstripe-omnipay": "^3@dev",