install: Check whether the system has at least 2GB RAM.
install: Check whether the system has at least 2GB RAM.

This should eliminate a common class of user error installing Zulip.

Fixes #2290, fixes #2320.

Juanvulcano/zulip,dattatreya303/zulip,arpith/zulip,eeshangarg/zulip,sonali0901/zulip,mahim97/zulip,susansls/zulip,mahim97/zulip,Juanvulcano/zulip,Juanvulcano/zulip,PhilSk/zulip,showell/zulip,hackerkid/zulip,niftynei/zulip,joyhchen/zulip,susansls/zulip,arpith/zulip,amanharitsh123/zulip,sharmaeklavya2/zulip,cosmicAsymmetry/zulip,timabbott/zulip,verma-varsha/zulip,blaze225/zulip,timabbott/zulip,PhilSk/zulip,brainwane/zulip,jainayush975/zulip,j831/zulip,zulip/zulip,PhilSk/zulip,Jianchun1/zulip,sharmaeklavya2/zulip,dhcrzf/zulip,sonali0901/zulip,KingxBanana/zulip,showell/zulip,samatdav/zulip,tommyip/zulip,jrowan/zulip,amanharitsh123/zulip,hackerkid/zulip,kou/zulip,brockwhittaker/zulip,synicalsyntax/zulip,hackerkid/zulip,tommyip/zulip,TigorC/zulip,peguin40/zulip,AZtheAsian/zulip,vabs22/zulip,rishig/zulip,dawran6/zulip,SmartPeople/zulip,brockwhittaker/zulip,vabs22/zulip,susansls/zulip,sonali0901/zulip,showell/zulip,rishig/zulip,ryanbackman/zulip,vabs22/zulip,vaidap/zulip,brockwhittaker/zulip,zacps/zulip,rht/zulip,dattatreya303/zulip,jrowan/zulip,dhcrzf/zulip,brainwane/zulip,eeshangarg/zulip,dawran6/zulip,blaze225/zulip,andersk/zulip,jackrzhang/zulip,amyliu345/zulip,sonali0901/zulip,souravbadami/zulip,KingxBanana/zulip,peguin40/zulip,joyhchen/zulip,eeshangarg/zulip,brainwane/zulip,dhcrzf/zulip,christi3k/zulip,j831/zulip,PhilSk/zulip,showell/zulip,dawran6/zulip,samatdav/zulip,andersk/zulip,dhcrzf/zulip,niftynei/zulip,niftynei/zulip,rht/zulip,JPJPJPOPOP/zulip,rht/zulip,TigorC/zulip,jrowan/zulip,tommyip/zulip,jainayush975/zulip,jphilipsen05/zulip,dawran6/zulip,rishig/zulip,shubhamdhama/zulip,TigorC/zulip,grave-w-grave/zulip,vabs22/zulip,dawran6/zulip,arpith/zulip,aakash-cr7/zulip,aakash-cr7/zulip,AZtheAsian/zulip,grave-w-grave/zulip,punchagan/zulip,jphilipsen05/zulip,kou/zulip,zulip/zulip,jackrzhang/zulip,jainayush975/zulip,Juanvulcano/zulip,PhilSk/zulip,zulip/zulip,punchagan/zulip,mahim97/zulip,Galexrt/zulip,grave-w-grave/zulip,brockwhittaker/zulip,peguin40/zulip,punchagan/zulip,rht/zulip,dattatreya303/zulip,KingxBanana/zulip,Juanvulcano/zulip,cosmicAsymmetry/zulip,JPJPJPOPOP/zulip,joyhchen/zulip,KingxBanana/zulip,jrowan/zulip,verma-varsha/zulip,tommyip/zulip,aakash-cr7/zulip,jainayush975/zulip,j831/zulip,tommyip/zulip,synicalsyntax/zulip,isht3/zulip,AZtheAsian/zulip,amanharitsh123/zulip,isht3/zulip,hackerkid/zulip,amanharitsh123/zulip,vaidap/zulip,AZtheAsian/zulip,kou/zulip,cosmicAsymmetry/zulip,samatdav/zulip,souravbadami/zulip,Galexrt/zulip,verma-varsha/zulip,niftynei/zulip,verma-varsha/zulip,isht3/zulip,brainwane/zulip,eeshangarg/zulip,dhcrzf/zulip,jphilipsen05/zulip,grave-w-grave/zulip,Diptanshu8/zulip,Galexrt/zulip,souravbadami/zulip,dattatreya303/zulip,timabbott/zulip,synicalsyntax/zulip,zulip/zulip,dattatreya303/zulip,arpith/zulip,hackerkid/zulip,vabs22/zulip,aakash-cr7/zulip,joyhchen/zulip,amyliu345/zulip,zacps/zulip,amyliu345/zulip,synicalsyntax/zulip,showell/zulip,Galexrt/zulip,hackerkid/zulip,JPJPJPOPOP/zulip,amyliu345/zulip,rishig/zulip,dattatreya303/zulip,zacps/zulip,cosmicAsymmetry/zulip,sharmaeklavya2/zulip,vaidap/zulip,niftynei/zulip,rht/zulip,shubhamdhama/zulip,rht/zulip,cosmicAsymmetry/zulip,christi3k/zulip,Diptanshu8/zulip,ryanbackman/zulip,kou/zulip,brainwane/zulip,isht3/zulip,aakash-cr7/zulip,isht3/zulip,Jianchun1/zulip,punchagan/zulip,andersk/zulip,souravbadami/zulip,ryanbackman/zulip,shubhamdhama/zulip,jrowan/zulip,hackerkid/zulip,Galexrt/zulip,synicalsyntax/zulip,PhilSk/zulip,vaidap/zulip,susansls/zulip,SmartPeople/zulip,TigorC/zulip,j831/zulip,eeshangarg/zulip,AZtheAsian/zulip,eeshangarg/zulip,blaze225/zulip,KingxBanana/zulip,timabbott/zulip,zacps/zulip,tommyip/zulip,Diptanshu8/zulip,amyliu345/zulip,susansls/zulip,jackrzhang/zulip,zacps/zulip,brockwhittaker/zulip,dhcrzf/zulip,christi3k/zulip,jphilipsen05/zulip,mahim97/zulip,TigorC/zulip,cosmicAsymmetry/zulip,verma-varsha/zulip,Juanvulcano/zulip,jackrzhang/zulip,timabbott/zulip,j831/zulip,synicalsyntax/zulip,amanharitsh123/zulip,SmartPeople/zulip,jainayush975/zulip,ryanbackman/zulip,eeshangarg/zulip,ryanbackman/zulip,peguin40/zulip,vaidap/zulip,samatdav/zulip,jackrzhang/zulip,j831/zulip,dawran6/zulip,christi3k/zulip,zulip/zulip,Jianchun1/zulip,isht3/zulip,SmartPeople/zulip,timabbott/zulip,shubhamdhama/zulip,andersk/zulip,JPJPJPOPOP/zulip,samatdav/zulip,JPJPJPOPOP/zulip,souravbadami/zulip,amanharitsh123/zulip,brainwane/zulip,rishig/zulip,AZtheAsian/zulip,jphilipsen05/zulip,punchagan/zulip,Jianchun1/zulip,Galexrt/zulip,jackrzhang/zulip,rishig/zulip,jphilipsen05/zulip,mahim97/zulip,sharmaeklavya2/zulip,rishig/zulip,brockwhittaker/zulip,JPJPJPOPOP/zulip,zulip/zulip,christi3k/zulip,sharmaeklavya2/zulip,sharmaeklavya2/zulip,kou/zulip,souravbadami/zulip,joyhchen/zulip,dhcrzf/zulip,showell/zulip,KingxBanana/zulip,sonali0901/zulip,arpith/zulip,shubhamdhama/zulip,peguin40/zulip,Jianchun1/zulip,synicalsyntax/zulip,samatdav/zulip,amyliu345/zulip,peguin40/zulip,grave-w-grave/zulip,brainwane/zulip,ryanbackman/zulip,shubhamdhama/zulip,andersk/zulip,vabs22/zulip,shubhamdhama/zulip,niftynei/zulip,verma-varsha/zulip,arpith/zulip,grave-w-grave/zulip,jainayush975/zulip,SmartPeople/zulip,sonali0901/zulip,TigorC/zulip,kou/zulip,kou/zulip,aakash-cr7/zulip,SmartPeople/zulip,Diptanshu8/zulip,jackrzhang/zulip,mahim97/zulip,rht/zulip,jrowan/zulip,Jianchun1/zulip,Diptanshu8/zulip,tommyip/zulip,christi3k/zulip,joyhchen/zulip,blaze225/zulip,blaze225/zulip,andersk/zulip,Galexrt/zulip,timabbott/zulip,punchagan/zulip,blaze225/zulip,susansls/zulip,Diptanshu8/zulip,andersk/zulip,vaidap/zulip,zulip/zulip,zacps/zulip,punchagan/zulip,showell/zulip