use pkg_resources

This change uses if no path for e capabilities-file is supplied a
temporary file created by pkg_resources, which should be more robust
than directly accessing the file. (This failed sometimes, for example
in zipped distributions or uncommon structures)

setup.cfg

@@ -40,6 +40,7 @@ install_requires =
     qrcode>=4.0
     pyserial
     python-barcode>=0.9.1,<1
+    setuptools
     six
     appdirs
     PyYAML