DOC: add section on versioning to devguide.
DOC: add section on versioning to devguide.

[ci skip]

josephcslater/scipy,zerothi/scipy,pbrod/scipy,WarrenWeckesser/scipy,sriki18/scipy,gfyoung/scipy,befelix/scipy,befelix/scipy,behzadnouri/scipy,argriffing/scipy,kalvdans/scipy,anntzer/scipy,rgommers/scipy,pbrod/scipy,apbard/scipy,Stefan-Endres/scipy,niknow/scipy,nonhermitian/scipy,rgommers/scipy,apbard/scipy,mdhaber/scipy,person142/scipy,anielsen001/scipy,arokem/scipy,anntzer/scipy,rgommers/scipy,grlee77/scipy,pschella/scipy,maniteja123/scipy,kleskjr/scipy,aeklant/scipy,niknow/scipy,jakevdp/scipy,andyfaff/scipy,anntzer/scipy,matthew-brett/scipy,zerothi/scipy,aeklant/scipy,gertingold/scipy,jjhelmus/scipy,dominicelse/scipy,woodscn/scipy,anielsen001/scipy,gertingold/scipy,niknow/scipy,josephcslater/scipy,perimosocordiae/scipy,matthewalbani/scipy,rgommers/scipy,jamestwebber/scipy,rgommers/scipy,kalvdans/scipy,grlee77/scipy,endolith/scipy,vigna/scipy,vigna/scipy,mikebenfield/scipy,aarchiba/scipy,jor-/scipy,mikebenfield/scipy,pbrod/scipy,scipy/scipy,gdooper/scipy,sriki18/scipy,mdhaber/scipy,pyramania/scipy,tylerjereddy/scipy,endolith/scipy,nmayorov/scipy,e-q/scipy,niknow/scipy,gdooper/scipy,dominicelse/scipy,jor-/scipy,Newman101/scipy,ilayn/scipy,gertingold/scipy,behzadnouri/scipy,kleskjr/scipy,jor-/scipy,kalvdans/scipy,argriffing/scipy,lhilt/scipy,befelix/scipy,haudren/scipy,gertingold/scipy,apbard/scipy,pizzathief/scipy,niknow/scipy,woodscn/scipy,aarchiba/scipy,nmayorov/scipy,bkendzior/scipy,mikebenfield/scipy,perimosocordiae/scipy,matthew-brett/scipy,bkendzior/scipy,nonhermitian/scipy,arokem/scipy,jor-/scipy,gertingold/scipy,behzadnouri/scipy,behzadnouri/scipy,grlee77/scipy,jamestwebber/scipy,matthew-brett/scipy,andyfaff/scipy,lhilt/scipy,josephcslater/scipy,aarchiba/scipy,kleskjr/scipy,jakevdp/scipy,haudren/scipy,bkendzior/scipy,anielsen001/scipy,argriffing/scipy,WarrenWeckesser/scipy,Eric89GXL/scipy,nmayorov/scipy,jor-/scipy,jjhelmus/scipy,scipy/scipy,andyfaff/scipy,gdooper/scipy,anntzer/scipy,Stefan-Endres/scipy,anntzer/scipy,maniteja123/scipy,tylerjereddy/scipy,arokem/scipy,Stefan-Endres/scipy,sriki18/scipy,dominicelse/scipy,jjhelmus/scipy,pizzathief/scipy,ilayn/scipy,matthewalbani/scipy,surhudm/scipy,tylerjereddy/scipy,scipy/scipy,ilayn/scipy,pizzathief/scipy,woodscn/scipy,mikebenfield/scipy,maniteja123/scipy,pyramania/scipy,josephcslater/scipy,gdooper/scipy,andyfaff/scipy,zerothi/scipy,bkendzior/scipy,jjhelmus/scipy,arokem/scipy,argriffing/scipy,jamestwebber/scipy,endolith/scipy,andyfaff/scipy,aeklant/scipy,gfyoung/scipy,niknow/scipy,matthewalbani/scipy,pizzathief/scipy,behzadnouri/scipy,josephcslater/scipy,Stefan-Endres/scipy,aeklant/scipy,pschella/scipy,apbard/scipy,lhilt/scipy,person142/scipy,haudren/scipy,pizzathief/scipy,endolith/scipy,jakevdp/scipy,Newman101/scipy,argriffing/scipy,e-q/scipy,nonhermitian/scipy,kleskjr/scipy,person142/scipy,e-q/scipy,pyramania/scipy,scipy/scipy,andyfaff/scipy,jamestwebber/scipy,Eric89GXL/scipy,sriki18/scipy,scipy/scipy,person142/scipy,Newman101/scipy,ilayn/scipy,bkendzior/scipy,Eric89GXL/scipy,grlee77/scipy,surhudm/scipy,mdhaber/scipy,woodscn/scipy,lhilt/scipy,kleskjr/scipy,Eric89GXL/scipy,Stefan-Endres/scipy,aarchiba/scipy,lhilt/scipy,surhudm/scipy,pbrod/scipy,pschella/scipy,matthew-brett/scipy,perimosocordiae/scipy,vigna/scipy,anielsen001/scipy,mdhaber/scipy,aarchiba/scipy,grlee77/scipy,scipy/scipy,befelix/scipy,haudren/scipy,sriki18/scipy,apbard/scipy,ilayn/scipy,argriffing/scipy,woodscn/scipy,maniteja123/scipy,woodscn/scipy,maniteja123/scipy,pyramania/scipy,Newman101/scipy,matthewalbani/scipy,WarrenWeckesser/scipy,zerothi/scipy,dominicelse/scipy,e-q/scipy,surhudm/scipy,arokem/scipy,perimosocordiae/scipy,gfyoung/scipy,tylerjereddy/scipy,kleskjr/scipy,behzadnouri/scipy,sriki18/scipy,befelix/scipy,haudren/scipy,pschella/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,zerothi/scipy,perimosocordiae/scipy,jjhelmus/scipy,aeklant/scipy,anielsen001/scipy,gdooper/scipy,endolith/scipy,anntzer/scipy,Newman101/scipy,kalvdans/scipy,tylerjereddy/scipy,ilayn/scipy,matthewalbani/scipy,pbrod/scipy,jakevdp/scipy,jakevdp/scipy,surhudm/scipy,haudren/scipy,nmayorov/scipy,nonhermitian/scipy,nonhermitian/scipy,matthew-brett/scipy,pschella/scipy,Newman101/scipy,zerothi/scipy,pbrod/scipy,WarrenWeckesser/scipy,vigna/scipy,endolith/scipy,anielsen001/scipy,mikebenfield/scipy,vigna/scipy,WarrenWeckesser/scipy,mdhaber/scipy,kalvdans/scipy,Eric89GXL/scipy,e-q/scipy,gfyoung/scipy,surhudm/scipy,jamestwebber/scipy,mdhaber/scipy,pyramania/scipy,Eric89GXL/scipy,nmayorov/scipy,maniteja123/scipy,gfyoung/scipy,perimosocordiae/scipy,dominicelse/scipy,person142/scipy