SSL, PHP7 support, etc.

【Contents of revision】
■Support for SSL
■Support for PHP7
■Fixed an error that sometimes appears in the theme options screen.

The following files have been modified for this update.
【Fixed files】
admin/theme-options.php
widget/recent_post.php
widget/recommend_post.php
header.php
style.css

For more information, please visit the download site for purchasers of Grider (tcd015).