Use Travis' phpunit

Author: bcrowe

.travis.yml

@@ -13,6 +13,5 @@ before_script:
   - echo "extension = mongo.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
   - composer self-update
   - composer install --dev -o
-  - composer require 'phpunit/phpunit=3.7.*'
 
-script: ./vendor/phpunit/phpunit/composer/bin/phpunit --coverage-text
+script: phpunit --coverage-text