Adds Plugin inside `repo` test project
Adds `repo` plugin detection.
Adds error message if wordpress path was not detected.
Fixes exclude paths flag passed to Ctags.

* Using `--exclude foo` doesn't work everywhere, but `--exclude=foo`
  does work. So switch to it instead.
Adds error message, if trying to generate Ctags without a WordPress path.
Bumps version and updates changelog for 0.2.1.
Build 0.2.1
Merges branch 'release/0.2.1' into develop