Enabled php7.2 tests

.travis.yml

@@ -8,6 +8,7 @@ php:
   - 5.6
   - 7.0
   - 7.1
+  - 7.2
   - nightly
 
 matrix:
@@ -23,7 +24,7 @@ matrix:
 
 install:
   - |
-    if [[ $TRAVIS_PHP_VERSION != '7.1' && $TRAVIS_PHP_VERSION != hhv* ]]; then
+    if [[ $TRAVIS_PHP_VERSION != '7.1' && $TRAVIS_PHP_VERSION != '7.2' && $TRAVIS_PHP_VERSION != hhv* ]]; then
         # disable xdebug for performance reasons when code coverage is not needed
         # note: xdebug on hhvm is disabled by default
         phpenv config-rm xdebug.ini || echo "xdebug is not installed"