Add Sass and Twig support for Geshi filter syntax highlighting in Drupal

By using the version of Geshi found at https://github.com/easybook/geshi , Sass and Twig syntax highlighting can be added to text fields in Drupal. After adding the new version to the Drupal codebase, visit the Geshi module's admin form at admin/config/content/formats/geshifilter, expand the Geshi library version fieldset, and use the "Flush the GeSHi language definition cache" button so that the languages are available when configuring text formats.