Add a module entrypoint (#173)

* pip_audit: add __main__.py

* README: document entrypoints

* CHANGELOG: record changes

* __main__: mark entrypoint as `no cover`

CHANGELOG.md

@@ -15,6 +15,11 @@ All versions prior to 0.0.9 are untracked.
   when `pip-audit` is invoked in environment mode
   ([#148](https://github.com/trailofbits/pip-audit/pull/148))
 
+* CLI: The `pip-audit` CLI can now be accessed through `python -m pip_audit`.
+  All functionality is identical to the functionality provided by the
+  `pip-audit` entrypoint
+  ([#173](https://github.com/trailofbits/pip-audit/pull/173))
+
 ### Changed
 
 ### Fixed

README.md

@@ -24,6 +24,13 @@ python -m pip install pip-audit
 
 ## Usage
 
+You can run `pip-audit` as a standalone program, or via `python -m`:
+
+```bash
+pip-audit --help
+python -m pip_audit --help
+```
+
 <!-- @begin-pip-audit-help@ -->
 ```
 usage: pip-audit [-h] [-V] [-l] [-r REQUIREMENTS] [-f FORMAT] [-s SERVICE]

pip_audit/__main__.py

@@ -0,0 +1,8 @@
+"""
+The `python -m pip_audit` entrypoint.
+"""
+
+if __name__ == "__main__":  # pragma: no cover
+    from pip_audit._cli import audit
+
+    audit()