Added example for trafficvance using apikey

Author: Michael Svendsen

examples/trafficvance_apikey.py

@@ -0,0 +1,17 @@
+from zeep import Client, xsd
+
+API_KEY_TEST = 'YOUR_OWN_API_KEY'
+WSDL_TEST = 'https://apitest.trafficvance.com/?v3=system.wsdl'
+
+client = Client(WSDL)
+header = xsd.Element(
+    '{WSDL_TEST}AuthenticateRequest',
+    xsd.ComplexType([
+        xsd.Element(
+            '{WSDL_TEST}apiKey', xsd.String()
+        )
+    ])
+)
+header_value = header(apiKey=API_KEY_TEST)
+
+res = client.service.getServerTime(_soapheaders=[header_value])