Improve relation docs about to_sql and where_values_hash
Improve relation docs about to_sql and where_values_hash

* User class instead of Users.
* #where_values_hash does not change the value to downcase as the
  example was showing.

[ci skip]

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