Fixed Regex

Fixes wrong match of regex in prepend and append.
'append' => '<button class="fa fa-share">share</button>' would cause a
wrapping <i> breaking code.

View/Helper/Bs3HtmlHelper.php

@@ -95,7 +95,7 @@ public function icon($class, $options = array()) {
  */
 	public function getIconVendor($class) {
 		foreach ($this->_config['iconVendorPrefixes'] as $iconVendorPrefix) {
-			$regex = sprintf('/^%s-|\s%s-/', $iconVendorPrefix, $iconVendorPrefix);
+            $regex = sprintf('/^(?<!<"\')(%s[\s-]){1,}/', $iconVendorPrefix, $iconVendorPrefix);
 			if (preg_match($regex, $class)) {
 				return $iconVendorPrefix;
 			}