Use class_exists() guard for Featured_Content.
Merge pull request #1 from tierra/feature-content-guard

Use class_exists() guard for Featured_Content.

Necessary for wp-cli compatability, as wp-cli loads plugins -after- themes, as opposed to before like core does.

Implementing this in theme-tools.php rather than theme-tools/featured-content.php so as to maintain the file integrity of featured-content.php against its wpcom variant.

Props @tierra