Fix associations basics guide
Fix associations basics guide

The column naming conflict options will not be going away, since
they are also used to support associations based on arbitrary SQL
expressions.  So change the wording to reflect that.

offshore-safety/sequel,seeARMS/sequel,offshore-safety/sequel,seeARMS/sequel,reubano/sequel,nicohvi/sequel,nju520/sequel,davidbegin/sequel,knut2/sequel,gferguson-gd/sequel,nicohvi/sequel,beni55/sequel,yazshel/sequel,knut2/sequel,pfarrell/sequel,t-morgan/sequel,gferguson-gd/sequel,yazshel/sequel,uhoh-itsmaciek/sequel,reubano/sequel,mpalmer/sequel,nju520/sequel,davidbegin/sequel,beni55/sequel,offshore-safety/sequel,pfarrell/sequel,mpalmer/sequel,t-morgan/sequel,Marketcircle/sequel,uhoh-itsmaciek/sequel