4.0

This release brings a few - strictly speaking - not backwards-compatible little fixes and corrections, now backed by automatic tests. 🧪

Following issues were addressed:

• Implement tests (b9095bc)
• Fix the STRIPBLANKS_ALL option (plainly did not work because of a typo) (873035f)
• SOURCE_DIR's default has been changed from CMAKE_CURRENT_SOURCE_DIR to CMAKE_CURRENT_LIST_DIR (9679564)
• SOURCE_DIR now supports relative paths (relative to CMAKE_CURRENT_LIST_DIR) (9679564)
• Give the intermediary artifact .gresource.xml a better name so that it's not a hidden file. It is now called resources.gresource.xml. (d9c50bd)