Clean up gitignore

Author: einarf

.gitignore

@@ -1,11 +1,27 @@
-__pycache__
-/.idea
-/.tox
-/env
-/build
-/demosys_py.egg-info
-/dist
-.DS_Store
-/manage.py
-/testdemo
-/docs/build
+__pycache__
+
+# Build and test directories
+/.tox
+/build
+/demosys_py.egg-info
+/dist
+/docs/build
+
+# Libraries
+*.a
+*.DLL
+
+# virtual envs
+/env/
+/.env/
+/.venv/
+
+# Local dev project
+/manage.py
+/testdemo
+
+# IDE files
+/.idea
+
+# Misc
+.DS_Store