Added description field from XML to Venue pages post_meta

I've added to the description field to the Venues post_meta (Custom Fields) similar to the change earlier this week adding in the directions field. The Shows, Workshops, and Artist pages all previously included their corresponding description fields in post_meta, but not Venues. I also bumped the version number in the plugin, readme, and changelog. The plugin updater hasn't been picking up updates since 1.3.0, perhaps because the version number in README.md had not been updated for 1.3.1 or 1.3.2.