roots: Search form support for WordPress 3.6+

https://github.com/Foxaii/roots/commit/61f2296a75a721479777080aeb050ebbd48058e5
roots: fix Roots_Walker_Comment issue with WP 3.6

https://github.com/retlehs/roots/commit/27a44d14af9e8a0c4c7c1c23166d6a3be63218be