added String#to_date documentation to Rails 4 upgrade guide
added String#to_date documentation to Rails 4 upgrade guide

[ci skip]

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