Move phpunit.xml into root to make PHPUnit easier to run

This seems to be pretty standard. Can just run `vendor/bin/phpunit` without any arguments. Removes the need for `composer test` (which is not ideal anyway as it removes colours from the output).

framework/core/.travis.yml

@@ -17,7 +17,7 @@ before_script:
   - composer install
 
 script:
-  - vendor/bin/phpunit -c tests/phpunit.xml --coverage-clover=coverage.xml
+  - vendor/bin/phpunit --coverage-clover=coverage.xml
 
 notifications:
   email:

framework/core/composer.json

@@ -72,9 +72,6 @@
             "Tests\\": "tests/"
         }
     },
-    "scripts": {
-        "test": "vendor/bin/phpunit -c tests/phpunit.xml"
-    },
     "extra": {
         "branch-alias": {
             "dev-master": "0.1.x-dev"

framework/core/phpunit.xml

@@ -12,13 +12,8 @@
 
     <testsuites>
         <testsuite name="all">
-            <directory suffix="Test.php">./</directory>
+            <directory suffix="Test.php">./tests</directory>
         </testsuite>
     </testsuites>
 
-    <php>
-        <env name="APP_ENV" value="testing"/>
-        <env name="CACHE_DRIVER" value="array"/>
-    </php>
-
 </phpunit>