fix for 7.1

Author: adityapatadia

.travis.yml

@@ -111,13 +111,16 @@ public function __construct($filename)
 
         $finfo = finfo_open(FILEINFO_MIME_TYPE);
         $checkWebp = false;
-        if (strstr(finfo_file($finfo, $filename), 'image') === false || version_compare(PHP_VERSION, '7.1.0', '<')) {
-            if (strstr(file_get_contents($filename), 'WEBPVP8') !== false) {
+        if (strstr(finfo_file($finfo, $filename), 'image') === false) {
+            if (version_compare(PHP_VERSION, '7.0.0', '<=') && strstr(file_get_contents($filename), 'WEBPVP8') !== false) {
                 $checkWebp = true;
                 $this->source_type = IMAGETYPE_WEBP;
             } else {
                 throw new ImageResizeException('Unsupported file type');
             }
+        } elseif(strstr(finfo_file($finfo, $filename), 'image/webp')) {
+          $checkWebp = true;
+          $this->source_type = IMAGETYPE_WEBP;
         }
 
         if (!$image_info = getimagesize($filename, $this->source_info)) {