removed es6 default params from gravatar method
removed es6 default params from gravatar method

3 duplicate issues in 1 month because many people are still running Node.js 4 or 5.

https://github.com/sahat/hackathon-starter/issues/607
https://github.com/sahat/hackathon-starter/issues/597
https://github.com/sahat/hackathon-starter/issues/604

crystalrood/piggie,bowdenk7/express-typescript-starter,awarn/bitcoins-trader,Yixuan-Angela/hackathon-starter,awarn/bitcoins-trader,awarn/cashier-analytics,ericmreid/pingypong,HappyGenes/HappyGenes,dafyddPrys/contingency,OperationSpark/Hackathon-Angel,colleenDunlap/Lake-Map,tendermario/binners-project,colleenDunlap/PlayingOnInternet,quazar11/portfolio,CahalKearney/node-boilerplate,stenio123/ai-hackathon,CAYdenberg/wikode,bowdenk7/express-typescript-starter,vymarkov/hackathon-starter,OperationSpark/Hackathon-Angel,CAYdenberg/wikode,niallobrien/hackathon-starter-plus,dborncamp/shuttles,dafyddPrys/contingency,peterblazejewicz/hackathon-starter,peterblazejewicz/hackathon-starter,quazar11/portfolio,vymarkov/hackathon-starter,Yixuan-Angela/hackathon-starter,sahat/hackathon-starter,wfpc92/cleansuit-backend,colleenDunlap/PlayingOnInternet,dborncamp/shuttles,JessedeGit/vegtable,crystalrood/piggie,stenio123/ai-hackathon,wfpc92/cleansuit-backend,ReadingPlus/flog,bowdenk7/express-typescript-starter,HappyGenes/HappyGenes,erood/weight_tracker_app,JessedeGit/vegtable,devneel/spitsomebars,devneel/spitsomebars,niallobrien/hackathon-starter-plus,sahat/hackathon-starter,gurneyman/riToolkit,ericmreid/pingypong,ak-zul/hackathon-starter,ak-zul/hackathon-starter,peterblazejewicz/hackathon-starter,gurneyman/riToolkit,tendermario/binners-project,colleenDunlap/PlayingOnInternet,colleenDunlap/Lake-Map,colleenDunlap/Lake-Map,crystalrood/piggie,sahat/hackathon-starter,ReadingPlus/flog,awarn/cashier-analytics,erood/weight_tracker_app,CahalKearney/node-boilerplate