Add version test

Because we hard-code the version twice, we want to make sure that the
VERSION file and the tzdata.__version__ attribute never get out of sync.

Author: pganssle

tests/test_version.py

@@ -0,0 +1,13 @@
+import os
+
+import tzdata
+
+REPO_ROOT = os.path.split(os.path.split(__file__)[0])[0]
+VERSION_FILE = os.path.join(REPO_ROOT, "VERSION")
+
+
+def test_version():
+    with open(VERSION_FILE, "rt") as f:
+        version_from_file = f.read()
+
+    assert version_from_file == tzdata.__version__