Do variable expanding on paths correctly

Now not only ``$HOME`` is substituted correctly but also all other env vars
like ``$PWD`` and others.

yfav

@@ -49,7 +49,7 @@ class Config(ConfigParser.ConfigParser):
 			return default
 
 def path(*path):
-	return os.path.join(*[os.path.expanduser(segment.replace("$HOME", "~")) for segment in path])
+	return os.path.join(*[os.path.expanduser(os.path.expandvars(segment)) for segment in path])
 
 DATA_DIR     = path(os.getenv("XDG_DATA_HOME",   "~/.local/share"), "yfav")
 CONFIG_FILE  = path(os.getenv("XDG_CONFIG_HOME", "~/.config"),      "yfav") # never used