Add __aenter__/__aexit__ for 3.5+ only
Add __aenter__/__aexit__ for 3.5+ only

elastic-coders/aiohttp,jashandeep-sohi/aiohttp,AraHaanOrg/aiohttp,alex-eri/aiohttp-1,flying-sheep/aiohttp,decentfox/aiohttp,z2v/aiohttp,decentfox/aiohttp,arthurdarcet/aiohttp,panda73111/aiohttp,singulared/aiohttp,rutsky/aiohttp,KeepSafe/aiohttp,esaezgil/aiohttp,KeepSafe/aiohttp,Srogozins/aiohttp,hellysmile/aiohttp,jettify/aiohttp,AraHaanOrg/aiohttp,pfreixes/aiohttp,mind1master/aiohttp,arthurdarcet/aiohttp,vaskalas/aiohttp,vaskalas/aiohttp,jashandeep-sohi/aiohttp,esaezgil/aiohttp,rutsky/aiohttp,playpauseandstop/aiohttp,vaskalas/aiohttp,panda73111/aiohttp,jashandeep-sohi/aiohttp,pfreixes/aiohttp,arthurdarcet/aiohttp,z2v/aiohttp,moden-py/aiohttp,moden-py/aiohttp,elastic-coders/aiohttp,Eyepea/aiohttp,rutsky/aiohttp,esaezgil/aiohttp,decentfox/aiohttp,jettify/aiohttp,Insoleet/aiohttp,moden-py/aiohttp,alex-eri/aiohttp-1,singulared/aiohttp,alex-eri/aiohttp-1,juliatem/aiohttp,elastic-coders/aiohttp,mind1master/aiohttp,juliatem/aiohttp,mind1master/aiohttp,KeepSafe/aiohttp,panda73111/aiohttp,jettify/aiohttp,hellysmile/aiohttp,singulared/aiohttp,z2v/aiohttp