Add tests for timezone (#363)

After #163, this adds some test data to check if the datetime objects
return the correct timezone
diff --git a/lib/yaml/constructor.py b/lib/yaml/constructor.py
index 568613b..8ce3972 100644
--- a/lib/yaml/constructor.py
+++ b/lib/yaml/constructor.py
@@ -23,7 +23,7 @@
     def __init__(self, offset):
         self._offset = offset
         seconds = abs(offset).total_seconds()
-        self._name = '%s%02d:%02d' % (
+        self._name = 'UTC%s%02d:%02d' % (
             '-' if offset.days < 0 else '+',
             seconds // 3600,
             seconds % 3600 // 60
diff --git a/tests/data/timestamp-bugs.code b/tests/data/timestamp-bugs.code
index b1d6e9c..e2c84cc 100644
--- a/tests/data/timestamp-bugs.code
+++ b/tests/data/timestamp-bugs.code
@@ -1,8 +1,8 @@
 [
-    datetime.datetime(2001, 12, 15, 3, 29, 43, 100000),
-    datetime.datetime(2001, 12, 14, 16, 29, 43, 100000),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 1010),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(60, "+1")),
-    datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(-90, "-1:30")),
-    datetime.datetime(2005, 7, 8, 17, 35, 4, 517600),
+    [datetime.datetime(2001, 12, 15, 3, 29, 43, 100000), 'UTC-05:30'],
+    [datetime.datetime(2001, 12, 14, 16, 29, 43, 100000), 'UTC+05:30'],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 1010), None],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(60, "+1")), 'UTC+01:00'],
+    [datetime.datetime(2001, 12, 14, 21, 59, 43, 0, FixedOffset(-90, "-1:30")), 'UTC-01:30'],
+    [datetime.datetime(2005, 7, 8, 17, 35, 4, 517600), None],
 ]
diff --git a/tests/data/timestamp-bugs.data b/tests/data/timestamp-bugs.data
index 721d290..b243d0d 100644
--- a/tests/data/timestamp-bugs.data
+++ b/tests/data/timestamp-bugs.data
@@ -1,6 +1,12 @@
-- 2001-12-14 21:59:43.10 -5:30
-- 2001-12-14 21:59:43.10 +5:30
-- 2001-12-14 21:59:43.00101
-- 2001-12-14 21:59:43+1
-- 2001-12-14 21:59:43-1:30
-- 2005-07-08 17:35:04.517600
+- !MyTime
+  - 2001-12-14 21:59:43.10 -5:30
+- !MyTime
+  - 2001-12-14 21:59:43.10 +5:30
+- !MyTime
+  - 2001-12-14 21:59:43.00101
+- !MyTime
+  - 2001-12-14 21:59:43+1
+- !MyTime
+  - 2001-12-14 21:59:43-1:30
+- !MyTime
+  - 2005-07-08 17:35:04.517600
diff --git a/tests/lib/test_constructor.py b/tests/lib/test_constructor.py
index 9e6c856..a22fd18 100644
--- a/tests/lib/test_constructor.py
+++ b/tests/lib/test_constructor.py
@@ -41,7 +41,18 @@
     def represent1(representer, native):
         return representer.represent_mapping("!tag1", native.__dict__)
 
+    def my_time_constructor(constructor, node):
+        seq = constructor.construct_sequence(node)
+        dt = seq[0]
+        tz = None
+        try:
+            tz = dt.tzinfo.tzname(dt)
+        except:
+            pass
+        return [dt, tz]
+
     yaml.add_constructor("!tag1", construct1, Loader=MyLoader)
+    yaml.add_constructor("!MyTime", my_time_constructor, Loader=MyLoader)
     yaml.add_representer(MyTestClass1, represent1, Dumper=MyDumper)
 
     class MyTestClass2(MyTestClass1, yaml.YAMLObject):
diff --git a/tests/lib3/test_constructor.py b/tests/lib3/test_constructor.py
index 3d69649..877982d 100644
--- a/tests/lib3/test_constructor.py
+++ b/tests/lib3/test_constructor.py
@@ -38,7 +38,18 @@
     def represent1(representer, native):
         return representer.represent_mapping("!tag1", native.__dict__)
 
+    def my_time_constructor(constructor, node):
+        seq = constructor.construct_sequence(node)
+        dt = seq[0]
+        tz = None
+        try:
+            tz = dt.tzinfo.tzname(dt)
+        except:
+            pass
+        return [dt, tz]
+
     yaml.add_constructor("!tag1", construct1, Loader=MyLoader)
+    yaml.add_constructor("!MyTime", my_time_constructor, Loader=MyLoader)
     yaml.add_representer(MyTestClass1, represent1, Dumper=MyDumper)
 
     class MyTestClass2(MyTestClass1, yaml.YAMLObject):