Added support for 'post__in' and 'post__not_in' for production listings (see #55).
Added a test for excluding categories in production listings (see #49).
Removed the 'day', 'month' and 'category filters from WPT_Events::load and WPT_Production::load.
Category filter now follow the WP_Query format: `cat`, `category_name`, `category__in` and `category__not_in'.
Added `post__in` and `post__not_in` filters for productions.
Merge branch 'master' into issue-55-exclude-productions
Added `post__in` and `post__not_in' filters tests for productions.
Fixed a bug where sticky productions were still showing when filtering produciton listings by categories or posts.
Merge branch 'issue-55-exclude-productions' into v0.8.4
Updated the readme.txt for v0.9.
Added a test for the new category attributes in the `wpt_events` shortcode.