Updated the DTS_Switcher::build_html_link() method to be a little cleaner / more logical. As a result now the ?theme=tablet query variables are appended to other query variables, i.e. site.com?page_id=3&theme=tablet.
Corrected an issue where widgets calling DTS_Switcher::build_html_link() would not properly pass an array() for $css_classes thus producing a PHP Warning when array_unshift() would receive $css_classes
Updated the plugin to 2.7 and documented the changes in the readme changelogs