Disable/hide email button for authors 

who haven't published in the previous six months.

Applies to https://github.com/GigaOM/gigaom/issues/4939
From what plugin/source does `get_the_author_meta` get the `'date_checked'` and `'post_date'` values?  [`get_the_author_meta()`](http://codex.wordpress.org/Function_Reference/get_the_author_meta) doesn't have those values from baseline WP unless I'm misreading somehow.