Make travis cache node_modules to speed up builds
Make travis cache node_modules to speed up builds

fatso83/Sinon.JS,timwienk/sinon,timwienk/sinon,jishi/sinon,cjohansen/Sinon.JS,cjohansen/Sinon.JS,fatso83/Sinon.JS,Khan/Sinon.JS,Khan/Sinon.JS,Khan/Sinon.JS,jishi/sinon,andpor/sinon,mroderick/Sinon.JS,andpor/sinon,jishi/sinon,cjohansen/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS,timwienk/sinon,mroderick/Sinon.JS,andpor/sinon