Enforce "en" lang in tests.

Some tests compare the result to english strings.

Do not test UnixCommandExecutor on Windows.

PharTest: explain why PHAR writing test are skipped.

InstallCommandTest: mock checkRequirements to allow the tests to run.

Run php_parallel_lint before all other tests.

Close #846

composer.json

@@ -41,12 +41,16 @@
         "monolog/monolog": "~1.6",
         "pimple/pimple": "~1.1",
         "robmorgan/phinx": "~0.4",
-        "sensiolabs/ansi-to-html": "~1.1"
+        "sensiolabs/ansi-to-html": "~1.1",
+        "jakub-onderka/php-parallel-lint": "0.8.*"
+    },
+
+    "autoload-dev": {
+        "psr-4": { "Tests\\PHPCI\\": "Tests/PHPCI" }
     },
 
     "require-dev": {
-        "phpunit/phpunit": "~4.0",
-        "phpspec/prophecy-phpunit": "~1.0",
+        "phpunit/phpunit": "~4.5",
         "phpmd/phpmd": "~2.0",
         "squizlabs/php_codesniffer": "~2.0",
         "block8/php-docblock-checker": "~1.0",