Increment version to v2.1.0 and add Python2.x deprecation warning (#458)

* Increment version and add Python2.x deprecation warning

Change test to actually test no warnings when on python3

flake8 compliant

* fix development status classifier

tests/unit/test_vcr_import.py

@@ -0,0 +1,16 @@
+import sys
+
+
+def test_vcr_import_deprecation(recwarn):
+
+    if 'vcr' in sys.modules:
+        # Remove imported module entry if already loaded in another test
+        del sys.modules['vcr']
+
+    import vcr  # noqa: F401
+
+    if sys.version_info[0] == 2:
+        assert len(recwarn) == 1
+        assert issubclass(recwarn[0].category, DeprecationWarning)
+    else:
+        assert len(recwarn) == 0