Add error type to `ExceptionRecord`. (#836)

So it's easier for parsers to get this info.
diff --git a/mobly/records.py b/mobly/records.py
index f4ec4d5..de7eb69 100644
--- a/mobly/records.py
+++ b/mobly/records.py
@@ -217,6 +217,7 @@
 
   Attributes:
     exception: Exception object, the original Exception.
+    type: string, type name of the exception object.
     stacktrace: string, stacktrace of the Exception.
     extras: optional serializable, this corresponds to the
       `TestSignal.extras` field.
@@ -226,6 +227,7 @@
 
   def __init__(self, e, position=None):
     self.exception = e
+    self.type = type(e).__name__
     self.stacktrace = None
     self.extras = None
     self.position = position
diff --git a/tests/mobly/records_test.py b/tests/mobly/records_test.py
index f3758f5..1c00044 100755
--- a/tests/mobly/records_test.py
+++ b/tests/mobly/records_test.py
@@ -406,6 +406,7 @@
     new_er = copy.deepcopy(er)
     self.assertIsNot(er, new_er)
     self.assertDictEqual(er.to_dict(), new_er.to_dict())
+    self.assertEqual(er.type, 'RecordTestError')
 
   def test_add_controller_info_record(self):
     tr = records.TestResult()