Revert "Condition that screen be a post or page not needed"

This reverts commit 87c34559bc36aa82dece5c065c845d7771fe06f0.
Merge branch 'experimental'
Merge branch 'custom-post-type-fix'
Merge branch 'custom-post-type-fix' into experimental
Merge branch 'experimental'
Merge branch 'master' of https://github.com/chapmanu/wp-meta-box-factory