Fix encoding-related issues in Name

There were a couple of bugs in the decoding logic for parts of
the high-level Name class.  This fixes them.

Fixes #81

gssapi/names.py

@@ -112,7 +112,7 @@ def __str__(self):
 
     def __unicode__(self):
         # Python 2 -- someone asked for unicode
-        return self.__bytes__().encode(_utils._get_encoding())
+        return self.__bytes__().decode(_utils._get_encoding())
 
     def __bytes__(self):
         # Python 3 -- someone asked for bytes
@@ -142,8 +142,8 @@ def display_as(self, name_type):
             raise NotImplementedError("Your GSSAPI implementation does not "
                                       "support RFC 6680 (the GSSAPI naming "
                                       "extensions)")
-        return rname_rfc6680.display_name_ext(self, name_type).encode(
-            _utils.get_encoding())
+        return rname_rfc6680.display_name_ext(self, name_type).decode(
+            _utils._get_encoding())
 
     @property
     def name_type(self):

gssapi/tests/test_high_level.py

@@ -396,6 +396,22 @@ def test_create_from_token(self):
         name2.shouldnt_be_none()
         name2.name_type.should_be(gb.NameType.kerberos_principal)
 
+    @_extension_test('rfc6680', 'RFC 6680')
+    def test_display_as(self):
+        name = gssnames.Name(TARGET_SERVICE_NAME,
+                             gb.NameType.hostbased_service)
+        canonical_name = name.canonicalize(gb.MechType.kerberos)
+
+        # NB(directxman12): krb5 doesn't implement display_name_ext, so just
+        # check to make sure we return the right types and a reasonable value
+        krb_name = canonical_name.display_as(
+            gb.NameType.hostbased_service)
+
+        princ_str = SERVICE_PRINCIPAL.decode('utf-8') + '@'
+        six.text_type(canonical_name).should_be(princ_str)
+        krb_name.should_be_a(six.text_type)
+        krb_name.should_be(princ_str)
+
     @_extension_test('rfc6680', 'RFC 6680')
     def test_create_from_composite_token_no_attrs(self):
         name1 = gssnames.Name(TARGET_SERVICE_NAME,