expanded crawling primer with examples, and applied other suggestions from the review
expanded crawling primer with examples, and applied other suggestions from the review

eLRuLL/scrapy,pablohoffman/scrapy,jdemaeyer/scrapy,darkrho/scrapy-scrapy,pfctdayelise/scrapy,snowdream1314/scrapy,lacrazyboy/scrapy,pablohoffman/scrapy,famorted/scrapy,hansenDise/scrapy,pawelmhm/scrapy,cleydson/scrapy,jdemaeyer/scrapy,URXtech/scrapy,zorojean/scrapy,mlyundin/scrapy,pombredanne/scrapy,fafaman/scrapy,ssteo/scrapy,cyberplant/scrapy,cursesun/scrapy,profjrr/scrapy,kmike/scrapy,wangjun/scrapy,GregoryVigoTorres/scrapy,crasker/scrapy,mgedmin/scrapy,nowopen/scrapy,mlyundin/scrapy,zhangtao11/scrapy,AaronTao1990/scrapy,eliasdorneles/scrapy,ArturGaspar/scrapy,irwinlove/scrapy,elacuesta/scrapy,nikgr95/scrapy,URXtech/scrapy,dangra/scrapy,zjuwangg/scrapy,github-account-because-they-want-it/scrapy,rolando/scrapy,KublaikhanGeek/scrapy,elacuesta/scrapy,taito/scrapy,z-fork/scrapy,kimimj/scrapy,webmakin/scrapy,CodeJuan/scrapy,rootAvish/scrapy,umrashrf/scrapy,kazitanvirahsan/scrapy,Bourneer/scrapy,yusofm/scrapy,dracony/scrapy,nguyenhongson03/scrapy,coderabhishek/scrapy,aivarsk/scrapy,kashyap32/scrapy,webmakin/scrapy,jiezhu2007/scrapy,rolando/scrapy,ENjOyAbLE1991/scrapy,pawelmhm/scrapy,tliber/scrapy,rolando-contrib/scrapy,pfctdayelise/scrapy,scorphus/scrapy,Allianzcortex/scrapy,Adai0808/scrapy-1,raphaelfruneaux/scrapy,webmakin/scrapy,IvanGavran/scrapy,elijah513/scrapy,curita/scrapy,yidongliu/scrapy,stenskjaer/scrapy,tntC4stl3/scrapy,ArturGaspar/scrapy,dracony/scrapy,hectoruelo/scrapy,foromer4/scrapy,Bourneer/scrapy,arush0311/scrapy,olorz/scrapy,cyrixhero/scrapy,cleydson/scrapy,wujuguang/scrapy,Bourneer/scrapy,profjrr/scrapy,TarasRudnyk/scrapy,CodeJuan/scrapy,github-account-because-they-want-it/scrapy,fafaman/scrapy,Djlavoy/scrapy,Zephor5/scrapy,Parlin-Galanodel/scrapy,finfish/scrapy,1yvT0s/scrapy,huoxudong125/scrapy,elijah513/scrapy,hyrole/scrapy,dgillis/scrapy,moraesnicol/scrapy,dracony/scrapy,rahulsharma1991/scrapy,barraponto/scrapy,nguyenhongson03/scrapy,rootAvish/scrapy,dangra/scrapy,nfunato/scrapy,godfreyy/scrapy,rolando/scrapy,tliber/scrapy,livepy/scrapy,IvanGavran/scrapy,jc0n/scrapy,kalessin/scrapy,stenskjaer/scrapy,zhangtao11/scrapy,zackslash/scrapy,starrify/scrapy,heamon7/scrapy,kashyap32/scrapy,legendtkl/scrapy,Djlavoy/scrapy,wzyuliyang/scrapy,olorz/scrapy,foromer4/scrapy,barraponto/scrapy,johnardavies/scrapy,pfctdayelise/scrapy,Chenmxs/scrapy,redapple/scrapy,farhan0581/scrapy,taito/scrapy,hbwzhsh/scrapy,moraesnicol/scrapy,z-fork/scrapy,KublaikhanGeek/scrapy,bmess/scrapy,tntC4stl3/scrapy,IvanGavran/scrapy,xiao26/scrapy,snowdream1314/scrapy,amboxer21/scrapy,CodeJuan/scrapy,livepy/scrapy,yusofm/scrapy,legendtkl/scrapy,ENjOyAbLE1991/scrapy,agreen/scrapy,darkrho/scrapy-scrapy,avtoritet/scrapy,Djlavoy/scrapy,JacobStevenR/scrapy,elijah513/scrapy,wenyu1001/scrapy,GregoryVigoTorres/scrapy,agusc/scrapy,ylcolala/scrapy,aivarsk/scrapy,cleydson/scrapy,pranjalpatil/scrapy,ylcolala/scrapy,OpenWhere/scrapy,heamon7/scrapy,Geeglee/scrapy,Adai0808/scrapy-1,codebhendi/scrapy,OpenWhere/scrapy,nikgr95/scrapy,godfreyy/scrapy,scrapy/scrapy,raphaelfruneaux/scrapy,Ryezhang/scrapy,fafaman/scrapy,Ryezhang/scrapy,cursesun/scrapy,liyy7/scrapy,csalazar/scrapy,tntC4stl3/scrapy,shaform/scrapy,umrashrf/scrapy,farhan0581/scrapy,curita/scrapy,agusc/scrapy,kmike/scrapy,JacobStevenR/scrapy,nfunato/scrapy,scrapy/scrapy,Lucifer-Kim/scrapy,wangjun/scrapy,jeffreyjinfeng/scrapy,zjuwangg/scrapy,fontenele/scrapy,Cnfc19932/scrapy,nowopen/scrapy,Preetwinder/scrapy,github-account-because-they-want-it/scrapy,zorojean/scrapy,dgillis/scrapy,fontenele/scrapy,fpy171/scrapy,wujuguang/scrapy,fpy171/scrapy,AaronTao1990/scrapy,pablohoffman/scrapy,stenskjaer/scrapy,redapple/scrapy,Zephor5/scrapy,zorojean/scrapy,rklabs/scrapy,Timeship/scrapy,tagatac/scrapy,YeelerG/scrapy,Parlin-Galanodel/scrapy,KublaikhanGeek/scrapy,liyy7/scrapy,Slater-Victoroff/scrapy,ssh-odoo/scrapy,Slater-Victoroff/scrapy,wangjun/scrapy,aivarsk/scrapy,kashyap32/scrapy,taito/scrapy,URXtech/scrapy,nikgr95/scrapy,JacobStevenR/scrapy,eliasdorneles/scrapy,rahulsharma1991/scrapy,WilliamKinaan/scrapy,pranjalpatil/scrapy,tliber/scrapy,irwinlove/scrapy,fqul/scrapy,famorted/scrapy,csalazar/scrapy,jc0n/scrapy,wenyu1001/scrapy,foromer4/scrapy,Chenmxs/scrapy,Allianzcortex/scrapy,Ryezhang/scrapy,rklabs/scrapy,songfj/scrapy,OpenWhere/scrapy,mgedmin/scrapy,w495/scrapy,hwsyy/scrapy,ssh-odoo/scrapy,mlyundin/scrapy,olafdietsche/scrapy,Digenis/scrapy,curita/scrapy,codebhendi/scrapy,starrify/scrapy,1yvT0s/scrapy,hwsyy/scrapy,1yvT0s/scrapy,haiiiiiyun/scrapy,legendtkl/scrapy,wzyuliyang/scrapy,mgedmin/scrapy,xiao26/scrapy,YeelerG/scrapy,rootAvish/scrapy,kmike/scrapy,crasker/scrapy,bmess/scrapy,agusc/scrapy,Lucifer-Kim/scrapy,irwinlove/scrapy,haiiiiiyun/scrapy,csalazar/scrapy,yarikoptic/scrapy,profjrr/scrapy,scorphus/scrapy,AaronTao1990/scrapy,rolando-contrib/scrapy,fqul/scrapy,Geeglee/scrapy,nfunato/scrapy,w495/scrapy,fpy171/scrapy,songfj/scrapy,eliasdorneles/scrapy,Lucifer-Kim/scrapy,johnardavies/scrapy,hwsyy/scrapy,huoxudong125/scrapy,ylcolala/scrapy,hectoruelo/scrapy,codebhendi/scrapy,tagatac/scrapy,dacjames/scrapy,scorphus/scrapy,wujuguang/scrapy,dgillis/scrapy,w495/scrapy,tagatac/scrapy,WilliamKinaan/scrapy,Preetwinder/scrapy,umrashrf/scrapy,kimimj/scrapy,Timeship/scrapy,ssteo/scrapy,crasker/scrapy,rolando-contrib/scrapy,avtoritet/scrapy,heamon7/scrapy,darkrho/scrapy-scrapy,Preetwinder/scrapy,eLRuLL/scrapy,elacuesta/scrapy,jeffreyjinfeng/scrapy,Digenis/scrapy,agreen/scrapy,yidongliu/scrapy,jdemaeyer/scrapy,coderabhishek/scrapy,lacrazyboy/scrapy,TarasRudnyk/scrapy,dacjames/scrapy,kazitanvirahsan/scrapy,ENjOyAbLE1991/scrapy,redapple/scrapy,ArturGaspar/scrapy,Adai0808/scrapy-1,TarasRudnyk/scrapy,amboxer21/scrapy,yidongliu/scrapy,olafdietsche/scrapy,Geeglee/scrapy,Parlin-Galanodel/scrapy,Cnfc19932/scrapy,jiezhu2007/scrapy,cyrixhero/scrapy,agreen/scrapy,yarikoptic/scrapy,olafdietsche/scrapy,cyberplant/scrapy,xiao26/scrapy,Timeship/scrapy,WilliamKinaan/scrapy,farhan0581/scrapy,carlosp420/scrapy,cyrixhero/scrapy,arush0311/scrapy,johnardavies/scrapy,finfish/scrapy,eLRuLL/scrapy,fontenele/scrapy,olorz/scrapy,godfreyy/scrapy,pombredanne/scrapy,rklabs/scrapy,wzyuliyang/scrapy,kazitanvirahsan/scrapy,songfj/scrapy,avtoritet/scrapy,bmess/scrapy,huoxudong125/scrapy,wenyu1001/scrapy,YeelerG/scrapy,kimimj/scrapy,Slater-Victoroff/scrapy,amboxer21/scrapy,GregoryVigoTorres/scrapy,cyberplant/scrapy,kalessin/scrapy,nowopen/scrapy,moraesnicol/scrapy,ssh-odoo/scrapy,rahulsharma1991/scrapy,dacjames/scrapy,lacrazyboy/scrapy,haiiiiiyun/scrapy,Digenis/scrapy,smaty1/scrapy,carlosp420/scrapy,Allianzcortex/scrapy,hyrole/scrapy,starrify/scrapy,raphaelfruneaux/scrapy,Chenmxs/scrapy,shaform/scrapy,jc0n/scrapy,pranjalpatil/scrapy,Cnfc19932/scrapy,kalessin/scrapy,dangra/scrapy,jeffreyjinfeng/scrapy,carlosp420/scrapy,coderabhishek/scrapy,z-fork/scrapy,cursesun/scrapy,barraponto/scrapy,arush0311/scrapy,yusofm/scrapy,pombredanne/scrapy,famorted/scrapy,hbwzhsh/scrapy,hbwzhsh/scrapy,zhangtao11/scrapy,fqul/scrapy,shaform/scrapy,liyy7/scrapy,zackslash/scrapy,zackslash/scrapy,zjuwangg/scrapy,ssteo/scrapy,hectoruelo/scrapy,smaty1/scrapy,hyrole/scrapy,jiezhu2007/scrapy,finfish/scrapy,Zephor5/scrapy,nguyenhongson03/scrapy,scrapy/scrapy,smaty1/scrapy,hansenDise/scrapy,livepy/scrapy,pawelmhm/scrapy,hansenDise/scrapy,snowdream1314/scrapy,yarikoptic/scrapy