Fixed error in XDG Compliance

This solves issue #87 that is related to XDG compliance.  The error was
related to cases where the XDG_DATA_HOME environment variable was defined.
In fact, if XDG_DATA_HOME was defined, then PATH_KB would be set to
$XDG_DATA_HOME and PATH_KB_GIT would be set to $XDG_DATA_HOME/.git,
rather than $XDG_DATA_HOME/kb and $XDG_DATA_HOME/kb/.git, respectively.

kb/config.py

@@ -18,7 +18,8 @@
 from pathlib import Path
 import toml
 
-BASE_PATH = os.environ.get("XDG_DATA_HOME",Path(Path.home(),".local","share","kb"))
+BASE_PATH = Path(os.environ.get("XDG_DATA_HOME",Path(Path.home(),".local","share")),"kb")
+
 
 DEFAULT_CONFIG = {
     "PATH_KB": str(Path(BASE_PATH)),