fix PSR2

Author: Joel Day

src/PhpPresentation/Style/Color.php

@@ -96,7 +96,7 @@ public function getAlpha()
     {
         $alpha = 100;
         if (strlen($this->argb) >= 6) {
-            $dec = hexdec(substr($this->argb,0,2));
+            $dec = hexdec(substr($this->argb, 0, 2));
             $alpha = number_format(( $dec/255 ) * 100, 2);
         }
         return $alpha;