Add Railties info to 5.1 release notes
Add Railties info to 5.1 release notes

[ci skip]

betesh/rails,arunagw/rails,Sen-Zhang/rails,jeremy/rails,Envek/rails,BlakeWilliams/rails,mohitnatoo/rails,mechanicles/rails,rails/rails,starknx/rails,yawboakye/rails,pschambacher/rails,Vasfed/rails,esparta/rails,kmayer/rails,alecspopa/rails,baerjam/rails,bogdanvlviv/rails,EmmaB/rails-1,EmmaB/rails-1,felipecvo/rails,lcreid/rails,riseshia/railsguides.kr,BlakeWilliams/rails,tgxworld/rails,Stellenticket/rails,illacceptanything/illacceptanything,jeremy/rails,schuetzm/rails,repinel/rails,assain/rails,yasslab/railsguides.jp,maicher/rails,baerjam/rails,bogdanvlviv/rails,MSP-Greg/rails,yawboakye/rails,prathamesh-sonpatki/rails,lucasmazza/rails,arunagw/rails,ledestin/rails,prathamesh-sonpatki/rails,illacceptanything/illacceptanything,deraru/rails,kmayer/rails,yhirano55/rails,esparta/rails,mathieujobin/reduced-rails-for-travis,koic/rails,hanystudy/rails,Erol/rails,lcreid/rails,arunagw/rails,illacceptanything/illacceptanything,aditya-kapoor/rails,Edouard-chin/rails,yhirano55/rails,lcreid/rails,ngpestelos/rails,rossta/rails,georgeclaghorn/rails,ttanimichi/rails,joonyou/rails,tjschuck/rails,mechanicles/rails,MSP-Greg/rails,yasslab/railsguides.jp,mechanicles/rails,shioyama/rails,illacceptanything/illacceptanything,betesh/rails,felipecvo/rails,ledestin/rails,palkan/rails,palkan/rails,notapatch/rails,kddeisz/rails,illacceptanything/illacceptanything,mathieujobin/reduced-rails-for-travis,illacceptanything/illacceptanything,georgeclaghorn/rails,illacceptanything/illacceptanything,mohitnatoo/rails,gfvcastro/rails,deraru/rails,mohitnatoo/rails,kamipo/rails,tgxworld/rails,Erol/rails,illacceptanything/illacceptanything,rails/rails,untidy-hair/rails,Sen-Zhang/rails,jeremy/rails,starknx/rails,fabianoleittes/rails,xlymian/rails,MSP-Greg/rails,assain/rails,bradleypriest/rails,Vasfed/rails,aditya-kapoor/rails,EmmaB/rails-1,brchristian/rails,Edouard-chin/rails,Envek/rails,gcourtemanche/rails,joonyou/rails,gauravtiwari/rails,yalab/rails,tjschuck/rails,prathamesh-sonpatki/rails,jeremy/rails,georgeclaghorn/rails,riseshia/railsguides.kr,odedniv/rails,kirs/rails-1,pschambacher/rails,repinel/rails,felipecvo/rails,iainbeeston/rails,repinel/rails,travisofthenorth/rails,kirs/rails-1,brchristian/rails,kddeisz/rails,shioyama/rails,vipulnsward/rails,Edouard-chin/rails,fabianoleittes/rails,tjschuck/rails,kamipo/rails,alecspopa/rails,Vasfed/rails,mijoharas/rails,ttanimichi/rails,bogdanvlviv/rails,kmcphillips/rails,betesh/rails,kmayer/rails,gcourtemanche/rails,esparta/rails,mijoharas/rails,iainbeeston/rails,gauravtiwari/rails,palkan/rails,xlymian/rails,MSP-Greg/rails,matrinox/rails,kaspth/rails,pvalena/rails,betesh/rails,deraru/rails,Erol/rails,aditya-kapoor/rails,yahonda/rails,fabianoleittes/rails,kmcphillips/rails,ttanimichi/rails,lucasmazza/rails,brchristian/rails,rossta/rails,vipulnsward/rails,fabianoleittes/rails,Stellenticket/rails,kamipo/rails,eileencodes/rails,rails/rails,bradleypriest/rails,kmcphillips/rails,untidy-hair/rails,hanystudy/rails,Edouard-chin/rails,palkan/rails,BlakeWilliams/rails,mohitnatoo/rails,bradleypriest/rails,Envek/rails,utilum/rails,travisofthenorth/rails,arunagw/rails,tjschuck/rails,yahonda/rails,BlakeWilliams/rails,utilum/rails,yalab/rails,kirs/rails-1,odedniv/rails,eileencodes/rails,kmcphillips/rails,lcreid/rails,illacceptanything/illacceptanything,gfvcastro/rails,illacceptanything/illacceptanything,riseshia/railsguides.kr,pschambacher/rails,utilum/rails,notapatch/rails,tgxworld/rails,mathieujobin/reduced-rails-for-travis,travisofthenorth/rails,prathamesh-sonpatki/rails,shioyama/rails,rafaelfranca/omg-rails,yawboakye/rails,illacceptanything/illacceptanything,tgxworld/rails,yahonda/rails,illacceptanything/illacceptanything,pvalena/rails,yasslab/railsguides.jp,utilum/rails,rossta/rails,shioyama/rails,deraru/rails,vipulnsward/rails,bogdanvlviv/rails,matrinox/rails,notapatch/rails,Envek/rails,schuetzm/rails,joonyou/rails,matrinox/rails,kddeisz/rails,Stellenticket/rails,printercu/rails,yalab/rails,ngpestelos/rails,yhirano55/rails,Sen-Zhang/rails,Erol/rails,baerjam/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,gfvcastro/rails,gauravtiwari/rails,flanger001/rails,yhirano55/rails,flanger001/rails,printercu/rails,notapatch/rails,aditya-kapoor/rails,travisofthenorth/rails,kaspth/rails,eileencodes/rails,xlymian/rails,koic/rails,vipulnsward/rails,pvalena/rails,untidy-hair/rails,assain/rails,maicher/rails,joonyou/rails,georgeclaghorn/rails,koic/rails,repinel/rails,gcourtemanche/rails,assain/rails,schuetzm/rails,ngpestelos/rails,kaspth/rails,flanger001/rails,yahonda/rails,iainbeeston/rails,maicher/rails,eileencodes/rails,gfvcastro/rails,hanystudy/rails,pvalena/rails,mechanicles/rails,baerjam/rails,flanger001/rails,printercu/rails,rafaelfranca/omg-rails,iainbeeston/rails,Vasfed/rails,starknx/rails,kddeisz/rails,untidy-hair/rails,yalab/rails,odedniv/rails,alecspopa/rails,printercu/rails,lucasmazza/rails,riseshia/railsguides.kr,yawboakye/rails,illacceptanything/illacceptanything,rails/rails,yasslab/railsguides.jp,rafaelfranca/omg-rails,mijoharas/rails,Stellenticket/rails,ledestin/rails,esparta/rails,schuetzm/rails