minor #290 Fix tests after #246 was merged (header case normalization) (siwinski)
minor #290 Fix tests after #246 was merged (header case normalization) (siwinski)

This PR was merged into the 3.2-dev branch.

Discussion
----------

Fix tests after #246 was merged (header case normalization)

When #246 was merged (4471f18306f66cce4218db28d047afa27df65cfd), [tests started failing](https://travis-ci.org/FriendsOfPHP/Goutte/builds/176095879).  This pull requests adjusts the assert header case to fix the failed tests.

```
There were 2 failures:
1) Goutte\Tests\ClientTest::testResetHeaders
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    'X-Test' => 'test'
+    'x-test' => 'test'
 )
/home/travis/build/FriendsOfPHP/Goutte/Goutte/Tests/ClientTest.php:383
2) Goutte\Tests\ClientTest::testRestart
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    'X-Test' => 'test'
+    'x-test' => 'test'
 )
/home/travis/build/FriendsOfPHP/Goutte/Goutte/Tests/ClientTest.php:397
```

Commits
-------

c990361 Fix tests after #246 was merged (header case normalization)

FriendsOfPHP/Goutte