Bump version to 0.28.0.
Bump version to 0.28.0.

Changes:

* Add :extract option to git source handler.
  Using ":extract => :clone" with a :git source handler will clone the
  repository into the build directory.
* Ignore more relative dependencies in dependency inspector. (sewhyte / #111)
* Add support for extracting tar.xz files. (djhaskin987 / #109)

kisoku/fpm-cookery,glensc/fpm-cookery,ryansch/fpm-cookery,ryansch/fpm-cookery,cas-ei/fpm-cookery,devkid/fpm-cookery,glensc/fpm-cookery,devkid/fpm-cookery,cas-ei/fpm-cookery,kisoku/fpm-cookery