Support legacy PHP 5.3 through PHP 7.3+

Author: clue

.travis.yml

@@ -1,8 +1,24 @@
 language: php
+
 php:
-  - 5.3
+# - 5.3 # requires old distro, see below
+  - 5.4
+  - 5.5
   - 5.6
-  - hhvm
+  - 7.0
+  - 7.1
+  - 7.2
+  - 7.3
+
+# lock distro so future defaults will not break the build
+dist: trusty
+
+matrix:
+  include:
+    - php: 5.3
+      dist: precise
+
+sudo: false
 
 install:
   - composer install --no-interaction

README.md

@@ -36,16 +36,21 @@ See also the [examples](examples):
 
 ## Install
 
-The recommended way to install this library is [through composer](http://getcomposer.org). [New to composer?](http://getcomposer.org/doc/00-intro.md)
-
-```JSON
-{
-    "require": {
-        "clue/shell-react": "~0.2.0"
-    }
-}
+The recommended way to install this library is [through Composer](https://getcomposer.org).
+[New to Composer?](https://getcomposer.org/doc/00-intro.md)
+
+This will install the latest supported version:
+
+```bash
+$ composer require clue/shell-react:^0.2
 ```
 
+See also the [CHANGELOG](CHANGELOG.md) for details about version upgrades.
+
+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+.
+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