Fix test_events.py on Python 3.3: ssl.Purpose was introduced in Python 3.4
Fix test_events.py on Python 3.3: ssl.Purpose was introduced in Python 3.4

Martiusweb/asyncio,haypo/trollius,haypo/trollius,jashandeep-sohi/asyncio,fallen/asyncio,vxgmichel/asyncio,gvanrossum/asyncio,1st1/asyncio,manipopopo/asyncio,ajdavis/asyncio,manipopopo/asyncio,fallen/asyncio,gvanrossum/asyncio,Martiusweb/asyncio,Martiusweb/asyncio,jashandeep-sohi/asyncio,vxgmichel/asyncio,gsb-eng/asyncio,1st1/asyncio,manipopopo/asyncio,vxgmichel/asyncio,fallen/asyncio,ajdavis/asyncio,gsb-eng/asyncio,ajdavis/asyncio,haypo/trollius,1st1/asyncio,gvanrossum/asyncio,jashandeep-sohi/asyncio,gsb-eng/asyncio