Added support for deleting a label

Author: mnapoli

lib/Github/Api/Issue/Labels.php

@@ -33,6 +33,11 @@ public function create($username, $repository, array $params)
         return $this->post('repos/'.rawurlencode($username).'/'.rawurlencode($repository).'/labels', $params);
     }
 
+    public function deleteLabel($username, $repository, $label)
+    {
+        return $this->delete('repos/'.rawurlencode($username).'/'.rawurlencode($repository).'/labels/'.rawurlencode($label));
+    }
+
     public function add($username, $repository, $issue, $labels)
     {
         if (is_string($labels)) {

test/Github/Tests/Api/Issue/LabelsTest.php

@@ -6,7 +6,6 @@
 
 class LabelsTest extends TestCase
 {
-
     /**
      * @test
      */
@@ -76,6 +75,22 @@ public function shouldCreateLabelWithColor()
         $this->assertEquals($expectedValue, $api->create('KnpLabs', 'php-github-api', $data));
     }
 
+    /**
+     * @test
+     */
+    public function shouldDeleteLabel()
+    {
+        $expectedValue = array('someOutput');
+
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('delete')
+            ->with('repos/KnpLabs/php-github-api/labels/foo')
+            ->will($this->returnValue($expectedValue));
+
+        $this->assertEquals($expectedValue, $api->deleteLabel('KnpLabs', 'php-github-api', 'foo'));
+    }
+
     /**
      * @test
      */