Test on PHP 7.4

Also remove HHVM (who's using it?).

.gitattributes

@@ -1,7 +1,7 @@
 /.gitattributes export-ignore
 /.gitignore export-ignore
-/tests export-ignore
-/sandbox export-ignore
-/build.xml export-ignore
-/build.properties.dev export-ignore
 /.travis.yml export-ignore
+/build.properties.dev export-ignore
+/build.xml export-ignore
+/tests export-ignore
+/tools export-ignore

.travis.yml

@@ -1,25 +1,35 @@
-sudo: false
+os: linux
+dist: xenial
 language: php
-dist: trusty
+
 php:
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
-  - hhvm
-  - nightly
+    - 7.0
+    - 7.1
+    - 7.2
+    - 7.3
+    - 7.4
+    - nightly
+
+cache:
+    directories:
+        - $HOME/.composer/cache
+
+jobs:
+    fast_finish: true
+    allow_failures:
+        - php: nightly
+    include:
+        - php: 5.3
+          dist: precise
+        - php: 5.4
+          dist: precise
+        - php: 5.5
+          dist: trusty
+        - php: 5.6
+          dist: trusty
 
-matrix:
-  include:
-    - php: "5.3"
-      dist: precise
-  fast_finish: true
-  allow_failures:
-    - php: nightly
-    - php: hhvm
+install:
+    - composer install --prefer-dist --no-progress --no-suggest -o
 
 script:
-  - php -dshort_open_tag=Off -dmagic_quotes_gpc=Off tests/index.php
+    - php -dshort_open_tag=Off -dmagic_quotes_gpc=Off tests/index.php