Version subcommand

- Set aqt version by version.py generation
- Drop importlib and pkg_resources chunks of code

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

setup.py

@@ -2,4 +2,11 @@
 
 from setuptools import setup
 
-setup(use_scm_version={"local_scheme": "no-local-version"})
+setup(
+    use_scm_version={
+        "write_to": "aqt/version.py",
+        "write_to_template": '__version__ = "{version}"',
+        "tag_regex": r"^(?P<prefix>v)?(?P<version>[^\+]+)(?P<suffix>.*)?$",
+        "local_scheme": "no-local-version",
+    }
+)