Deleted /tags and /trunk

These must have been added with the switch from the wp.org SVN repo to GitHub. Your tags are all present in https://github.com/bmarshall511/wordpress-zero-spam/releases and /trunk directory is repetitive.

Personally I use https://github.com/GaryJones/wordpress-plugin-git-flow-svn-deploy
Merge pull request #8 from afragen/patch-2

Deleted /tags and /trunk