Adding HHVM to the testing matrix. Addresses #538
Adding HHVM to the testing matrix. Addresses #538

Naktibalda/guzzle,jabong/guzzle3,barryvdh/guzzle3,staylor/guzzle,paveljanda/guzzle,javierTerry/guzzle,stefanruijsenaars/guzzle,grokify/guzzle,paveljanda/guzzle,dawehner/guzzle,barryvdh/guzzle3,videni/guzzle,sulfo/guzzle,guzzle/guzzle,mustafavelioglu/guzzle,Rinat-wc/guzzle,Tobion/guzzle,mortenhauberg/guzzle,thinsoldier/guzzle,stea4lth/guzzle,jeskew/guzzle,lahmizzar/guzzle,staylor/guzzle,rajaehtesham/guzzle,kkopachev/guzzle,checat/guzzle,videni/guzzle,roundpartner/guzzle3,roundpartner/guzzle3,WebSeed/guzzle,grokify/guzzle,Briareos/guzzle,guzzle/guzzle,Tony133/guzzle,michabbb-backup/guzzle,guzzle/guzzle3,guzzle/guzzle3,chengky/guzzle,chengky/guzzle,ehough/guzzle,legovaer/guzzle3,thinsoldier/guzzle,phlogisticfugu/guzzle,WebSeed/guzzle,stefanruijsenaars/guzzle,duyhuynhngoc/guzzle,Brunty/guzzle,EdgarPE/guzzle,kminh/guzzle3,rajaehtesham/guzzle,rsauvatinet/guzzle3,atrauzzi/guzzle,Tobion/guzzle,mortenhauberg/guzzle,rsauvatinet/guzzle3,SharpSpring/guzzle3,mrm/guzzle,dawehner/guzzle,Briareos/guzzle,EdgarPE/guzzle,mubassirhayat/guzzle,kkopachev/guzzle,ehough/guzzle,vrkansagara/guzzle,vrkansagara/guzzle,checat/guzzle,Naktibalda/guzzle,dshafik/guzzle,Tony133/guzzle,SharpSpring/guzzle3,mustafavelioglu/guzzle,lahmizzar/guzzle,wherefortravel/guzzle,BostjanOb/guzzle,dawehner/guzzle,sahat/guzzle,hussainweb/guzzle,hussainweb/guzzle,duyhuynhngoc/guzzle,BostjanOb/guzzle,Rinat-wc/guzzle,dshafik/guzzle,legovaer/guzzle3,Brunty/guzzle,jabong/guzzle3,stea4lth/guzzle,mrm/guzzle,sulfo/guzzle,michabbb-backup/guzzle,kminh/guzzle3,nazo/guzzle,justincy/guzzle,justincy/guzzle,cenxun/guzzle,cenxun/guzzle,atrauzzi/guzzle,jeskew/guzzle,wherefortravel/guzzle,mikicaivosevic/guzzle,nazo/guzzle,javierTerry/guzzle,mikicaivosevic/guzzle,phlogisticfugu/guzzle