Parse styles contained within defs

fixes #98

Author: bsweeney

src/Svg/Document.php

@@ -401,7 +401,7 @@ function _tagEnd($parser, $name)
                 break;
         }
 
-        if (!$this->inDefs && $tag) {
+        if ((!$this->inDefs && $tag) || $tag instanceof StyleTag) {
             $tag->handleEnd();
         }
     }

src/Svg/Tag/AbstractTag.php

@@ -59,15 +59,15 @@ public function handle($attributes)
     {
         $this->attributes = $attributes;
 
-        if (!$this->getDocument()->inDefs) {
+        if (!$this->getDocument()->inDefs || $this instanceof StyleTag) {
             $this->before($attributes);
             $this->start($attributes);
         }
     }
 
     public function handleEnd()
     {
-        if (!$this->getDocument()->inDefs) {
+        if (!$this->getDocument()->inDefs || $this instanceof StyleTag) {
             $this->end();
             $this->after();
         }