Clean up .gitignore

Removed a lot of unused/irrelevant entries (they were from GitHub's
.gitignore template for Python projects) and kept only those that
are actually needed/used.

.gitignore

@@ -1,34 +1,8 @@
-# Byte-compiled / optimized / DLL files
+# Python bytecode
+*.py[co]
 __pycache__/
-*.py[cod]
-*$py.class
 
-# C extensions
-*.so
-
-# Distribution / packaging
-.Python
-env/
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
+# setuptools
 *.egg-info/
-.installed.cfg
-*.egg
-
-# Installer logs
-pip-log.txt
-pip-delete-this-directory.txt
-
-# virtualenv
-.venv/
-venv/
-ENV/
+build/
+dist/