Update phpunit configuration (webmozarts#104)

* Move verbose=true to config file, and remove it from cli options in ci
* Link to xsd for easy validation
* Remove redundant suffix option from test suite

.travis.yml

@@ -38,7 +38,7 @@ install:
   - composer update $COMPOSER_FLAGS --prefer-dist --no-interaction
 
 script:
-  - if [[ $COVERAGE = yes ]]; then vendor/bin/phpunit --verbose --coverage-clover=coverage.clover; else vendor/bin/phpunit --verbose; fi
+  - if [[ $COVERAGE = yes ]]; then vendor/bin/phpunit --coverage-clover=coverage.clover; else vendor/bin/phpunit; fi
 
 after_script:
   - if [[ $COVERAGE = yes ]]; then wget https://scrutinizer-ci.com/ocular.phar && php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi

phpunit.xml.dist

@@ -1,9 +1,14 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php" colors="true">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="./vendor/phpunit/phpunit/phpunit.xsd"
+        bootstrap="vendor/autoload.php"
+        colors="true"
+        verbose="true"
+>
     <testsuites>
         <testsuite name="Webmozart Assert Test Suite">
-            <directory suffix="Test.php">./tests/</directory>
+            <directory>./tests/</directory>
         </testsuite>
     </testsuites>