Add gitignore file

Pipfile.lock is ignored because it won't work between different
platforms if the dependency requirements diverge.

Python compilation products are ignored, as they are derived directly
from Python source files.

.gitignore

@@ -0,0 +1,7 @@
+# Doesn't work with platform differences
+Pipfile.lock
+
+# Python compilation products
+__pycache__/
+*.pyc
+*.pyo