Add version property (#418)

src/hats/__init__.py

@@ -1,4 +1,5 @@
 """High-level namespace, hats"""
 
 from . import catalog, inspection, io, pixel_math
+from ._version import __version__
 from .loaders import read_hats

tests/hats/test_version.py

@@ -0,0 +1,6 @@
+import hats
+
+
+def test_hats_version():
+    """Check to see that we can get the HATS version"""
+    assert hats.__version__ is not None