Add enum value to enum repr (#2126)

This changes enum reprs to look like `<Enum.name: value>` similarly to
the Python enum module.

This keeps the str of enums as `Enum.name`, like the Python enum module.
diff --git a/tests/test_enum.py b/tests/test_enum.py
index bfaa193..46cb379 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -7,6 +7,9 @@
     assert str(m.UnscopedEnum.EOne) == "UnscopedEnum.EOne"
     assert str(m.UnscopedEnum.ETwo) == "UnscopedEnum.ETwo"
     assert str(m.EOne) == "UnscopedEnum.EOne"
+    assert repr(m.UnscopedEnum.EOne) == "<UnscopedEnum.EOne: 1>"
+    assert repr(m.UnscopedEnum.ETwo) == "<UnscopedEnum.ETwo: 2>"
+    assert repr(m.EOne) == "<UnscopedEnum.EOne: 1>"
 
     # name property
     assert m.UnscopedEnum.EOne.name == "EOne"
@@ -143,6 +146,8 @@
 def test_implicit_conversion():
     assert str(m.ClassWithUnscopedEnum.EMode.EFirstMode) == "EMode.EFirstMode"
     assert str(m.ClassWithUnscopedEnum.EFirstMode) == "EMode.EFirstMode"
+    assert repr(m.ClassWithUnscopedEnum.EMode.EFirstMode) == "<EMode.EFirstMode: 1>"
+    assert repr(m.ClassWithUnscopedEnum.EFirstMode) == "<EMode.EFirstMode: 1>"
 
     f = m.ClassWithUnscopedEnum.test_function
     first = m.ClassWithUnscopedEnum.EFirstMode
@@ -167,7 +172,7 @@
     x[f(first)] = 3
     x[f(second)] = 4
     # Hashing test
-    assert str(x) == "{EMode.EFirstMode: 3, EMode.ESecondMode: 4}"
+    assert repr(x) == "{<EMode.EFirstMode: 1>: 3, <EMode.ESecondMode: 2>: 4}"
 
 
 def test_binary_operators():