Support legacy PHP 5.3 through PHP 7.2 and HHVM

.travis.yml

@@ -1,11 +1,29 @@
 language: php
+
 php:
-  - 5.6
-  - 5.5
+# - 5.3 # requires old distro, see below
   - 5.4
-  - 5.3
-  - hhvm
+  - 5.5
+  - 5.6
+  - 7.0
+  - 7.1
+  - 7.2
+  - hhvm # ignore errors, see below
+
+# lock distro so future defaults will not break the build
+dist: trusty
+
+matrix:
+  include:
+    - php: 5.3
+      dist: precise
+  allow_failures:
+    - php: hhvm
+
+sudo: false
+
 install:
-  - composer install --prefer-source --no-interaction
+  - composer install --no-interaction
+
 script:
   - vendor/bin/phpunit --coverage-text

README.md

@@ -16,6 +16,11 @@ The recommended way to install this library is [through composer](http://getcomp
 }
 ```
 
+This project aims to run on any platform and thus does not require any PHP
+extensions and supports running on legacy PHP 5.3 through current PHP 7+ and
+HHVM.
+It's *highly recommended to use PHP 7+* for this project.
+
 ## Tests
 
 To run the test suite, you first need to clone this repo and then install all