don't crash when the package version is unknown

when running the module directly from command line
without a python package, importlib doesn't know
the package version and this causes freetar to crash.

this commit assumes "development" as the version
if a version is not available, instead of crashing

freetar/utils.py

@@ -2,7 +2,10 @@
 
 
 def get_version():
-    return importlib.metadata.version(__package__)
+    try:
+        return importlib.metadata.version(__package__)
+    except importlib.metadata.PackageNotFoundError:
+        return 'development'
 
 
 class FreetarError(Exception):