Update Travis build config so new defaults do not break the build

.travis.yml

@@ -1,17 +1,27 @@
 language: php
 
 php:
-  - 5.3
+# - 5.3 # requires old distro, see below
   - 5.4
   - 5.5
   - 5.6
   - 7
-  - hhvm
+  - hhvm # ignore errors, see below
+
+# lock distro so new 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:
-  - phpunit --coverage-text
+  - vendor/bin/phpunit --coverage-text

README.md

@@ -43,6 +43,21 @@ $ composer require react/datagram:^1.1.1
 
 See also the [CHANGELOG](CHANGELOG.md) for details about version upgrades.
 
+## Tests
+
+To run the test suite, you first need to clone this repo and then install all
+dependencies [through Composer](http://getcomposer.org):
+
+```bash
+$ composer install
+```
+
+To run the test suite, go to the project root and run:
+
+```bash
+$ php vendor/bin/phpunit
+```
+
 ## License
 
 MIT

composer.json

@@ -21,6 +21,7 @@
         "react/promise": "~2.1|~1.2"
     },
     "require-dev": {
-        "clue/block-react": "~1.0"
+        "clue/block-react": "~1.0",
+        "phpunit/phpunit": "^5.0 || ^4.8"
     }
 }

tests/FactoryTest.php

@@ -162,7 +162,7 @@ public function testCancelCreateClientWithCancellableHostnameResolver()
 
     public function testCancelCreateClientWithUncancellableHostnameResolver()
     {
-        $promise = $this->getMock('React\Promise\PromiseInterface');
+        $promise = $this->getMockBuilder('React\Promise\PromiseInterface')->getMock();
         $this->resolver->expects($this->once())->method('resolve')->with('example.com')->willReturn($promise);
 
         $promise = $this->factory->createClient('example.com:0');

tests/bootstrap.php

@@ -26,7 +26,7 @@ protected function expectCallableNever()
 
     protected function createCallableMock()
     {
-        return $this->getMock('CallableStub');
+        return $this->getMockBuilder('CallableStub')->getMock();
     }
 
     protected function createResolverMock()