Relax Rack dependency
Relax Rack dependency

Rack is very carefully released, we should be able to upgrade minor
versions without much effort. We are a bunch of Rails core who are also
Rack core members so there won't be any issue with that. And in case
there's something wrong, we should fix on both sides.
Even though, doesn't seem like we will have a 1.7 version, this will be
useful as an example for when we go with Rack 2.0. We should ~> 2.0.

repinel/rails,bolek/rails,riseshia/railsguides.kr,palkan/rails,bradleypriest/rails,Erol/rails,amoody2108/TechForJustice,rossta/rails,arunagw/rails,yalab/rails,kddeisz/rails,Sen-Zhang/rails,kenta-s/rails,odedniv/rails,betesh/rails,bolek/rails,mtsmfm/railstest,felipecvo/rails,mtsmfm/rails,88rabbit/newRails,felipecvo/rails,prathamesh-sonpatki/rails,yalab/rails,EmmaB/rails-1,palkan/rails,bogdanvlviv/rails,mtsmfm/railstest,printercu/rails,tijwelch/rails,illacceptanything/illacceptanything,voray/rails,MichaelSp/rails,rails/rails,illacceptanything/illacceptanything,pschambacher/rails,mechanicles/rails,aditya-kapoor/rails,maicher/rails,ttanimichi/rails,MSP-Greg/rails,Erol/rails,coreyward/rails,lcreid/rails,baerjam/rails,notapatch/rails,betesh/rails,marklocklear/rails,pvalena/rails,flanger001/rails,gfvcastro/rails,stefanmb/rails,flanger001/rails,sergey-alekseev/rails,ngpestelos/rails,flanger001/rails,mathieujobin/reduced-rails-for-travis,vipulnsward/rails,Stellenticket/rails,brchristian/rails,sealocal/rails,matrinox/rails,eileencodes/rails,MSP-Greg/rails,mtsmfm/railstest,Spin42/rails,brchristian/rails,tgxworld/rails,mechanicles/rails,Edouard-chin/rails,jeremy/rails,mtsmfm/rails,schuetzm/rails,koic/rails,Vasfed/rails,aditya-kapoor/rails,jeremy/rails,rails/rails,marklocklear/rails,yhirano55/rails,gfvcastro/rails,stefanmb/rails,gcourtemanche/rails,kmayer/rails,vassilevsky/rails,untidy-hair/rails,bolek/rails,samphilipd/rails,printercu/rails,mathieujobin/reduced-rails-for-travis,kddeisz/rails,yawboakye/rails,koic/rails,kaspth/rails,arunagw/rails,rbhitchcock/rails,hanystudy/rails,mijoharas/rails,mtsmfm/rails,matrinox/rails,yasslab/railsguides.jp,vassilevsky/rails,maicher/rails,xlymian/rails,mijoharas/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,odedniv/rails,arunagw/rails,rossta/rails,yhirano55/rails,mijoharas/rails,mohitnatoo/rails,ledestin/rails,coreyward/rails,rbhitchcock/rails,Stellenticket/rails,tjschuck/rails,mohitnatoo/rails,yawboakye/rails,eileencodes/rails,Erol/rails,kmcphillips/rails,Sen-Zhang/rails,kamipo/rails,gfvcastro/rails,iainbeeston/rails,bogdanvlviv/rails,palkan/rails,baerjam/rails,baerjam/rails,lucasmazza/rails,gavingmiller/rails,printercu/rails,riseshia/railsguides.kr,georgeclaghorn/rails,ledestin/rails,rossta/rails,georgeclaghorn/rails,kmayer/rails,kamipo/rails,Envek/rails,tgxworld/rails,kachick/rails,Edouard-chin/rails,kamipo/rails,starknx/rails,fabianoleittes/rails,alecspopa/rails,tgxworld/rails,Spin42/rails,aditya-kapoor/rails,betesh/rails,joonyou/rails,printercu/rails,iainbeeston/rails,yahonda/rails,richseviora/rails,notapatch/rails,tgxworld/rails,betesh/rails,palkan/rails,rafaelfranca/omg-rails,shioyama/rails,yasslab/railsguides.jp,mohitnatoo/rails,tjschuck/rails,notapatch/rails,MichaelSp/rails,Envek/rails,elfassy/rails,rafaelfranca/omg-rails,vassilevsky/rails,kmayer/rails,aditya-kapoor/rails,tjschuck/rails,fabianoleittes/rails,shioyama/rails,esparta/rails,samphilipd/rails,illacceptanything/illacceptanything,BlakeWilliams/rails,travisofthenorth/rails,repinel/rails,Vasfed/rails,gcourtemanche/rails,vipulnsward/rails,starknx/rails,Sen-Zhang/rails,yalab/rails,pschambacher/rails,pvalena/rails,joonyou/rails,tijwelch/rails,kirs/rails-1,ngpestelos/rails,shioyama/rails,kmcphillips/rails,iainbeeston/rails,untidy-hair/rails,bradleypriest/rails,ngpestelos/rails,odedniv/rails,yahonda/rails,eileencodes/rails,joonyou/rails,EmmaB/rails-1,elfassy/rails,rails/rails,repinel/rails,gavingmiller/rails,mathieujobin/reduced-rails-for-travis,Erol/rails,bogdanvlviv/rails,sergey-alekseev/rails,yawboakye/rails,assain/rails,xlymian/rails,lcreid/rails,deraru/rails,kachick/rails,illacceptanything/illacceptanything,joonyou/rails,illacceptanything/illacceptanything,esparta/rails,alecspopa/rails,arjes/rails,starknx/rails,jeremy/rails,yhirano55/rails,richseviora/rails,vipulnsward/rails,amoody2108/TechForJustice,flanger001/rails,coreyward/rails,sealocal/rails,BlakeWilliams/rails,elfassy/rails,riseshia/railsguides.kr,hanystudy/rails,travisofthenorth/rails,ttanimichi/rails,gauravtiwari/rails,schuetzm/rails,rbhitchcock/rails,yhirano55/rails,rafaelfranca/omg-rails,illacceptanything/illacceptanything,kddeisz/rails,fabianoleittes/rails,schuetzm/rails,pvalena/rails,Envek/rails,notapatch/rails,koic/rails,Vasfed/rails,vipulnsward/rails,BlakeWilliams/rails,Envek/rails,BlakeWilliams/rails,gauravtiwari/rails,fabianoleittes/rails,georgeclaghorn/rails,lcreid/rails,georgeclaghorn/rails,yahonda/rails,Vasfed/rails,kenta-s/rails,Spin42/rails,deraru/rails,voray/rails,alecspopa/rails,riseshia/railsguides.kr,utilum/rails,illacceptanything/illacceptanything,lucasmazza/rails,stefanmb/rails,shioyama/rails,MSP-Greg/rails,88rabbit/newRails,illacceptanything/illacceptanything,kmcphillips/rails,ledestin/rails,prathamesh-sonpatki/rails,esparta/rails,voray/rails,deraru/rails,kirs/rails-1,pvalena/rails,utilum/rails,brchristian/rails,untidy-hair/rails,illacceptanything/illacceptanything,88rabbit/newRails,yalab/rails,kmcphillips/ra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