Added UnitTest data for TimeSpan

Author: ntziolis

RestSharp.Tests/SampleData/timespans.txt

@@ -0,0 +1,9 @@
+{
+    "Tick": "00:00:00.0468006",
+	"Millisecond": "00:00:00.1250000",
+    "Second": "00:00:08.0000000",
+    "Minute": "00:55:02.0000000",
+    "Hour": "21:30:07.0000000",
+    "NullableWithoutValue": null,
+    "NullableWithValue": "21:30:07.0000000",
+}