Add travis support for OS X tests and PHP 7.3 (#399)

Add travis support for OS X tests and PHP 7.3

- Also attempts to add support for Windows, but that is not passing so it has been set as "allowed to fail".

.travis.yml

@@ -1,30 +1,62 @@
-language: php
-
-dist: trusty
-sudo: false
-
 cache:
   directories:
     - $HOME/.composer/cache
 
+addons:
+  homebrew:
+    packages:
+    - php
+    - composer
+
 matrix:
+  allow_failures:
+    - os: windows
+      language: bash
   include:
-    - php: 7.2
+    - os: linux
+      dist: trusty
+      language: php
+      php: 7.2
       env:
         - DEPS=lowest
-    - php: 7.2
+    - os: linux
+      dist: trusty
+      language: php
+      php: 7.2
       env:
         - DEPS=locked
         - CHECK_CS=true
         - TEST_COVERAGE=true
         - CHECK_PHPSTAN=true
-    - php: 7.2
+    - os: linux
+      dist: trusty
+      language: php
+      php: 7.2
+      env:
+        - DEPS=latest
+    - os: linux
+      dist: trusty
+      language: php
+      php: 7.3
       env:
         - DEPS=latest
+    - os: windows
+      language: bash
+      env:
+        - DEPS=locked
+        - CHECK_CS=false
+        - TEST_COVERAGE=false
+        - CHECK_PHPSTAN=false
+    - os: osx
+      env:
+        - DEPS=locked
+        - CHECK_CS=false
+        - TEST_COVERAGE=false
+        - CHECK_PHPSTAN=false
 
 before_install:
   - travis_retry composer self-update
-  - phpenv config-rm xdebug.ini || true
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then phpenv config-rm xdebug.ini || true; fi
 
 install:
   - if [[ $DEPS == 'latest' ]]; then travis_retry composer update --no-interaction ; fi