Break tools out into their own dirs

tools/unify/BUILD

@@ -0,0 +1,7 @@
+py_binary(
+    name = "unify",
+    main = "__main__.py",
+    deps = [
+        py_requirement("unify"),
+    ]
+)

tools/unify/__main__.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python3
+
+"""
+Shim for executing isort.
+"""
+
+
+from unify import main
+
+
+if __name__ == "__main__":
+    exit(main())