DOC: update INSTALL.txt with info on binary installers and 32-bit Windows.
DOC: update INSTALL.txt with info on binary installers and 32-bit Windows.

Closes gh-5832.

[ci skip]

mattip/numpy,utke1/numpy,mwiebe/numpy,pbrod/numpy,MichaelAquilina/numpy,dimasad/numpy,BMJHayward/numpy,jonathanunderwood/numpy,felipebetancur/numpy,simongibbons/numpy,madphysicist/numpy,SiccarPoint/numpy,MSeifert04/numpy,gfyoung/numpy,skymanaditya1/numpy,ekalosak/numpy,MaPePeR/numpy,dimasad/numpy,MaPePeR/numpy,ESSS/numpy,grlee77/numpy,BabeNovelty/numpy,ContinuumIO/numpy,trankmichael/numpy,seberg/numpy,ChanderG/numpy,bertrand-l/numpy,kiwifb/numpy,seberg/numpy,pizzathief/numpy,dwillmer/numpy,pyparallel/numpy,sonnyhu/numpy,nguyentu1602/numpy,abalkin/numpy,groutr/numpy,chiffa/numpy,cjermain/numpy,bmorris3/numpy,ekalosak/numpy,Dapid/numpy,sonnyhu/numpy,has2k1/numpy,trankmichael/numpy,cjermain/numpy,mathdd/numpy,bringingheavendown/numpy,nguyentu1602/numpy,numpy/numpy,MaPePeR/numpy,bringingheavendown/numpy,GrimDerp/numpy,njase/numpy,has2k1/numpy,rudimeier/numpy,kirillzhuravlev/numpy,Anwesh43/numpy,ChristopherHogan/numpy,ddasilva/numpy,KaelChen/numpy,MSeifert04/numpy,KaelChen/numpy,mhvk/numpy,empeeu/numpy,felipebetancur/numpy,CMartelLML/numpy,rhythmsosad/numpy,AustereCuriosity/numpy,bmorris3/numpy,skwbc/numpy,nguyentu1602/numpy,kirillzhuravlev/numpy,anntzer/numpy,dwillmer/numpy,CMartelLML/numpy,mhvk/numpy,rherault-insa/numpy,dato-code/numpy,ESSS/numpy,Linkid/numpy,stuarteberg/numpy,sinhrks/numpy,jschueller/numpy,simongibbons/numpy,ssanderson/numpy,mattip/numpy,sinhrks/numpy,charris/numpy,rhythmsosad/numpy,numpy/numpy,Anwesh43/numpy,ahaldane/numpy,ssanderson/numpy,dimasad/numpy,gmcastil/numpy,bmorris3/numpy,dato-code/numpy,grlee77/numpy,WarrenWeckesser/numpy,mattip/numpy,ahaldane/numpy,empeeu/numpy,pyparallel/numpy,shoyer/numpy,argriffing/numpy,empeeu/numpy,SunghanKim/numpy,mathdd/numpy,MSeifert04/numpy,Yusa95/numpy,joferkington/numpy,musically-ut/numpy,dato-code/numpy,Yusa95/numpy,maniteja123/numpy,pyparallel/numpy,ViralLeadership/numpy,groutr/numpy,charris/numpy,leifdenby/numpy,maniteja123/numpy,drasmuss/numpy,pbrod/numpy,WarrenWeckesser/numpy,joferkington/numpy,musically-ut/numpy,chiffa/numpy,anntzer/numpy,tacaswell/numpy,endolith/numpy,WarrenWeckesser/numpy,madphysicist/numpy,SiccarPoint/numpy,chatcannon/numpy,jakirkham/numpy,jankoslavic/numpy,WillieMaddox/numpy,jorisvandenbossche/numpy,solarjoe/numpy,Linkid/numpy,rgommers/numpy,GaZ3ll3/numpy,SunghanKim/numpy,MSeifert04/numpy,felipebetancur/numpy,Srisai85/numpy,skymanaditya1/numpy,skymanaditya1/numpy,Srisai85/numpy,CMartelLML/numpy,ContinuumIO/numpy,endolith/numpy,nbeaver/numpy,mwiebe/numpy,musically-ut/numpy,rajathkumarmp/numpy,b-carter/numpy,solarjoe/numpy,pizzathief/numpy,cjermain/numpy,utke1/numpy,CMartelLML/numpy,dimasad/numpy,sonnyhu/numpy,ahaldane/numpy,moreati/numpy,trankmichael/numpy,gmcastil/numpy,abalkin/numpy,Eric89GXL/numpy,drasmuss/numpy,endolith/numpy,AustereCuriosity/numpy,Anwesh43/numpy,ChanderG/numpy,pdebuyl/numpy,ViralLeadership/numpy,sinhrks/numpy,rhythmsosad/numpy,musically-ut/numpy,jonathanunderwood/numpy,pizzathief/numpy,kiwifb/numpy,hainm/numpy,rajathkumarmp/numpy,KaelChen/numpy,skwbc/numpy,numpy/numpy,gmcastil/numpy,argriffing/numpy,BabeNovelty/numpy,Yusa95/numpy,rudimeier/numpy,jankoslavic/numpy,hainm/numpy,BabeNovelty/numpy,ESSS/numpy,ChanderG/numpy,bringingheavendown/numpy,MichaelAquilina/numpy,githubmlai/numpy,kiwifb/numpy,ChristopherHogan/numpy,GaZ3ll3/numpy,shoyer/numpy,chiffa/numpy,simongibbons/numpy,moreati/numpy,bmorris3/numpy,dato-code/numpy,rudimeier/numpy,mathdd/numpy,pdebuyl/numpy,ChanderG/numpy,shoyer/numpy,seberg/numpy,Linkid/numpy,has2k1/numpy,hainm/numpy,Srisai85/numpy,mingwpy/numpy,seberg/numpy,BMJHayward/numpy,joferkington/numpy,grlee77/numpy,ddasilva/numpy,bertrand-l/numpy,rgommers/numpy,jschueller/numpy,abalkin/numpy,Linkid/numpy,mhvk/numpy,ekalosak/numpy,empeeu/numpy,groutr/numpy,githubmlai/numpy,Eric89GXL/numpy,Anwesh43/numpy,simongibbons/numpy,stuarteberg/numpy,anntzer/numpy,nbeaver/numpy,Srisai85/numpy,GaZ3ll3/numpy,skymanaditya1/numpy,MSeifert04/numpy,KaelChen/numpy,nbeaver/numpy,BMJHayward/numpy,SunghanKim/numpy,rherault-insa/numpy,dwillmer/numpy,rgommers/numpy,b-carter/numpy,leifdenby/numpy,WarrenWeckesser/numpy,pizzathief/numpy,MaPePeR/numpy,tacaswell/numpy,GrimDerp/numpy,tynn/numpy,pbrod/numpy,SiccarPoint/numpy,dwillmer/numpy,stuarteberg/numpy,BabeNovelty/numpy,nguyentu1602/numpy,madphysicist/numpy,joferkington/numpy,behzadnouri/numpy,behzadnouri/numpy,MichaelAquilina/numpy,pdebuyl/numpy,felipebetancur/numpy,mingwpy/numpy,anntzer/numpy,grlee77/numpy,BMJHayward/numpy,AustereCuriosity/numpy,jorisvandenbossche/numpy,rgommers/numpy,simongibbons/numpy,madphysicist/numpy,shoyer/numpy,ahaldane/numpy,bertrand-l/numpy,tacaswell/numpy,rajathkumarmp/numpy,jorisvandenbossche/numpy,skwbc/numpy,mhvk/numpy,pizzathief/numpy,jschueller/numpy,jonathanunderwood/numpy,GaZ3ll3/numpy,ekalosak/numpy,tynn/numpy,kirillzhuravlev/numpy,gfyoung/numpy,utke1/numpy,jorisvandenbossche/numpy,mingwpy/numpy,behzadnouri/numpy,WarrenWeckesser/numpy,Eric89GXL/numpy,rudimeier/numpy,madphysicist/numpy,mwiebe/numpy,jorisvandenbossche/numpy,mattip/numpy,Eric89GXL/numpy,has2k1/numpy,stuarteberg/numpy,pdebuyl/numpy,Dapid/numpy,githubmlai/numpy,pbrod/numpy,jakirkham/numpy,charris/numpy,WillieMaddox/numpy,rhythmsosad/numpy,Yusa95/numpy,GrimDerp/numpy,ContinuumIO/numpy,njase/numpy,ChristopherHogan/numpy,ssanderson/numpy,pbrod/numpy,mingwpy/numpy,trankmichael/numpy,njase/numpy,hainm/numpy,jankoslavic/numpy,leifdenby/numpy,solarjoe/numpy,mhvk/numpy,sinhrks/numpy,numpy/numpy,ViralLeadership/numpy,drasmuss/numpy,jakirkham/numpy,b-carter/numpy,rherault-insa/numpy,chatcannon/numpy,kirillzhuravlev/numpy,maniteja123/numpy,charris/numpy,shoyer/numpy,cjermain/numpy,ddasilva/numpy,tynn/numpy,gfyoung/numpy,endolith/numpy,Dapid/numpy,sonnyhu/numpy,jakirkham/numpy,argriffing/numpy,chatcannon/numpy,ChristopherHogan/numpy,grlee77/numpy,WillieMaddox/numpy,jschueller/numpy,rajathkumarmp/numpy,ahaldane/numpy,MichaelAquilina/numpy,jakirkham/numpy,SunghanKim/numpy,mathdd/numpy,jankoslavic/numpy,GrimDerp/numpy,SiccarPoint/numpy,githubmlai/numpy,moreati/numpy