Fixes #702 -- allow _.escape to return empty strings for null and undefined
Fixes #702 -- allow _.escape to return empty strings for null and undefined

craigmichaelmartin/underscore,RepmujNetsik/underscore,irr/underscore,yuhualingfeng/underscore,jonot/underscore,AaronNGray/underscore-server,vincent1988/underscore,SerenoShen/underscore,xiaoqiang730730/underscore,colemakdvorak/underscore,gougouGet/underscore,LiskHQ/underscore,roychen-7/underscore,dyx/underscore,debutt/underscore,thiswildorchid/underscore,ligson/underscore,jianganglu/underscore,dyx/underscore,zabefloyd/underscore,cgvarela/underscore,akre54/underscore,Forever8/underscore,JonAbrams/underscore,kanso/underscore,singhsterabhi/underscore,lqjack/underscore,kwangkim/underscore,SeriaWei/underscore,roychen-7/underscore,dfurtado/underscore,Aplopio/underscore,ijidan/underscore,craigmichaelmartin/underscore,eaglesjava/underscore,thiswildorchid/underscore,wjb12/underscore,vinodbonala/underscore,youprofit/underscore,Aplopio/underscore,ryanwholey/underscore,amdjs/underscore,bkillenit/underscore,premkumargithub/underscore,huangnan1/2016gitStudy,veg/underscore,kuychaco/underscore,componentizr/underscore,michaelficarra/underscore,janocat/underscore,ThiagoGarciaAlves/underscore,strongconjunctions/underscore,akre54/underscore,thisismygithub/underscore,starterstep/underscore,mairasala/underscore,singhsterabhi/underscore,zhangguangyong/underscore,rlugojr/underscore,aziz-boudi4/underscore,documentcloud/underscore,mitar/underscore,LiskHQ/underscore,tnga/underscore-es,Feiyang1/underscore,falqas/underscore,megawac/underscore,Yangani/underscore,dimitriwalters/underscore,jdelbello/underscore,PUSEN/underscore,sdwang/underscore,falqas/underscore,PengShi-sp/underscore,prosenjit-itobuz/underscore,jridgewell/underscore,vincent1988/underscore,platinumazure/underscore,huzion/underscore,jpalomar/underscore,jpalomar/underscore,lis186/underscore,Gimcrack/underscore,vinodbonala/underscore,jolthoff/underscore,strongconjunctions/underscore,jridgewell/underscore,1800joe/underscore,1800joe/underscore,dkusch/underscore,Gimcrack/underscore,oss6/underscore,cnwhy/underscore,yekg880809/underscore,jordanwink201/underscore,veg/underscore,ligson/underscore,npmcomponent/jashkenas-underscore,greyhwndz/underscore,ereddate/underscore,huangnan1/2016gitStudy,Joanna913/underscore,RepmujNetsik/underscore,cintiamh/underscore,Yangani/underscore,platinumazure/underscore,ElseZhang/underscore,starterstep/underscore,michaelficarra/underscore,WangRex/underscore,greyhwndz/underscore,dfurtado/underscore,bkillenit/underscore,wxmfront/underscore,kairyan/underscore,jashkenas/underscore,ereddate/underscore,oss6/underscore,huzion/underscore,nickkneafsey/underscore,zhangguangyong/underscore,gougouGet/underscore,premkumargithub/underscore,amdjs/underscore,WangRex/underscore,prosenjit-itobuz/underscore,liminghui/underscore,jordanwink201/underscore,snackshen/underscore,xiaoqiang730730/underscore,tnga/underscore-es,Feiyang1/underscore,cgvarela/underscore,irr/underscore,polandeme/underscore,cailong1028/underscore,mjhasbach/underscore,ThiagoGarciaAlves/underscore,JonAbrams/underscore,wxmfront/underscore,documentcloud/underscore,imsingh/underscore,Tim-Zhang/underscore,jonot/underscore,beenlee/underscore,hackreactor/underscore,jiankers/underscore,lis186/underscore,JoaquinSiabra/underscore,jiankers/underscore,colemakdvorak/underscore,jashkenas/underscore,janocat/underscore,liyandalmllml/underscore,lqjack/underscore,AaronNGray/underscore-server,jdelbello/underscore,yuhualingfeng/underscore,SeriaWei/underscore,keepgoingwm/underscore,keepgoingwm/underscore,natac13/underscore,PUSEN/underscore,jfarid27/underscore,polandeme/underscore,mdboop/underscore,cnwhy/underscore,mitar/underscore,cintiamh/underscore,kuychaco/underscore,jianganglu/underscore,rlugojr/underscore,SerenoShen/underscore,lucasfanning/underscore,ElseZhang/underscore,PengShi-sp/underscore,JoaquinSiabra/underscore,appleboy/underscore,elancom/underscore,kwangkim/underscore,mdboop/underscore,mairasala/underscore,sdwang/underscore,hackreactor/underscore,debutt/underscore,snackshen/underscore,braddunbar/underscore,thisismygithub/underscore,liminghui/underscore,aziz-boudi4/underscore,jfarid27/underscore,Joanna913/underscore,imsingh/underscore,Tetpay/underscore,dkusch/underscore,yekg880809/underscore,emiel187/underscore,paulfalgout/underscore,zabefloyd/underscore,lucasfanning/underscore,kairyan/underscore,Forever8/underscore,ijidan/underscore,nickkneafsey/underscore,natac13/underscore,Tim-Zhang/underscore,dxuehu/underscore,mjhasbach/underscore,eaglesjava/underscore,liyandalmllml/underscore,kanso/underscore,jolthoff/underscore,ryanwholey/underscore,elancom/underscore,emiel187/underscore,dxuehu/underscore,beenlee/underscore,youprofit/underscore,wjb12/underscore