change headers to lowercase to make headers case-insensitive

Author: ekuwang

src/Qiniu/Http/Client.php

@@ -83,7 +83,7 @@ public static function sendRequest($request)
             CURLOPT_HEADER => true,
             CURLOPT_NOBODY => false,
             CURLOPT_CUSTOMREQUEST => $request->method,
-            CURLOPT_URL => $request->url
+            CURLOPT_URL => $request->url,
         );
 
         // Handle open_basedir & safe mode
@@ -129,7 +129,7 @@ private static function parseHeaders($raw)
             $headerLine = trim($line);
             $kv = explode(':', $headerLine);
             if (count($kv) > 1) {
-                $headers[$kv[0]] = trim($kv[1]);
+                $headers[strtolower($kv[0])] = trim($kv[1]);
             }
         }
         return $headers;

src/Qiniu/Http/Response.php

@@ -130,7 +130,7 @@ public function json()
 
     private static function bodyJson($body)
     {
-        return \Qiniu\json_decode((string)$body, true, 512);
+        return \Qiniu\json_decode((string) $body, true, 512);
     }
 
     public function xVia()
@@ -170,7 +170,7 @@ public function needRetry()
 
     private static function isJson($headers)
     {
-        return array_key_exists('Content-Type', $headers) &&
-        strpos($headers['Content-Type'], 'application/json') === 0;
+        return array_key_exists('content-type', $headers) &&
+        strpos($headers['content-type'], 'application/json') === 0;
     }
 }