Install libevent-dev on Travis and enable 7.2

.travis.yml

@@ -1,14 +1,25 @@
-sudo: false
+sudo: required
 
 language: php
 
+addons:
+  apt:
+    packages:
+    - libevent-dev
+
 php:
   - 5.5
   - 5.6
   - 7.0
   - 7.1
+  - 7.2
   - nightly
 
+matrix:
+  allow_failures:
+    - php: nightly
+  fast_finish: true
+
 install:
   - php -r 'exit((int) (PHP_MAJOR_VERSION < 7));' || (yes "" | pecl install "channel://pecl.php.net/libevent-0.1.0")
   - php -r 'exit((int) (PHP_MAJOR_VERSION < 7));' || (yes "" | pecl install ev)