Hotfix/post with json body

.travis.yml

@@ -1,6 +1,6 @@
language: php
php:
  - "5.3"
  - "5.5"

before_install:
  - composer self-update

README.md

@@ -96,4 +96,34 @@ echo $twitter->setGetfield($getfield)
    ->performRequest();
```

POST with JSON Request Example
-------------------

Set request header when calling performRequest();

```php
$url = 'https://api.twitter.com/1.1/direct_messages/events/new.json';
$postJson = [
    "event" => [
        "type" => "message_create",
        "message_create" => [
          "target" => [
            "recipient_id" => "TWITTER_ID"
          ],
          "message_data" => [
            "text" => "Hello World!",
          ]
        ]
    ]
];
$requestMethod = 'POST';

$twitter = new TwitterAPIExchange($settings);
echo $twitter->buildOauth($url, $requestMethod)
             ->performRequest(true,[
                CURLOPT_HTTPHEADER => array('Content-Type:application/json'),
                CURLOPT_POSTFIELDS => json_encode($postJson)
             ]);
```

That is it! Really simple, works great with the 1.1 API. Thanks to @lackovic10 and @rivers on SO!

TwitterAPIExchange.php

@@ -296,6 +296,14 @@ public function performRequest($return = true, $curlOptions = array())
            CURLOPT_TIMEOUT => 10,
        );


        if(isset($curlOptions[CURLOPT_HTTPHEADER])){  
            $options[CURLOPT_HTTPHEADER] = array_merge(
                $curlOptions[CURLOPT_HTTPHEADER],
                $header
            );
        }

        if (!is_null($postfields))
        {
            $options[CURLOPT_POSTFIELDS] = http_build_query($postfields, '', '&');

index.php

@@ -35,3 +35,27 @@
echo $twitter->setGetfield($getfield)
             ->buildOauth($url, $requestMethod)
             ->performRequest();

// /** Perform a POST request with content type "application/json" and echo the response **/
// /** Note: `DO NOT` Set the POST field. Use curl options in performRequest instead **/
$url = 'https://api.twitter.com/1.1/direct_messages/events/new.json';
$postJson = [
    "event" => [
        "type" => "message_create",
        "message_create" => [
          "target" => [
            "recipient_id" => "" // Twitter ID
          ],
          "message_data" => [
            "text" => "Hello World!",
          ]
        ]
    ]
];
$requestMethod = 'POST';
$twitter = new TwitterAPIExchange($settings);
echo $twitter->buildOauth($url, $requestMethod)
             ->performRequest(true,[
                CURLOPT_HTTPHEADER => array('Content-Type:application/json'),
                CURLOPT_POSTFIELDS => json_encode($postJson)
             ]);

test/TwitterAPIExchangeTest.php

@@ -105,10 +105,10 @@ public function testStatusesHomeTimeline()
    {
        $url    = 'https://api.twitter.com/1.1/statuses/home_timeline.json';
        $method = 'GET';
        $params = '?user_id=3232926711&max_id=756123701888839681';
        $params = '?user_id=3232926711&max_id=787407826176110600';

        $data     = $this->exchange->request($url, $method, $params);
        $expected = "Test Tweet";
        $expected = "TEST TWEET";

        $this->assertContains($expected, $data);
    }