setup.py: Add clasifiers, long_description
setup.py: Add clasifiers, long_description

setup.py can define metadata about the package. Some of it is
non-mandatory, but is useful for PyPi and elsewhere. As such, add a
long_description field (copied from current PyPi package, which was in
turn copied from the website) and a list of classifiers (based on the
current list on PyPi).

This fixes issue 2615.

MechCoder/sympy,mcdaniel67/sympy,asm666/sympy,debugger22/sympy,liangjiaxing/sympy,skidzo/sympy,cswiercz/sympy,Curious72/sympy,MechCoder/sympy,Vishluck/sympy,grevutiu-gabriel/sympy,saurabhjn76/sympy,madan96/sympy,atsao72/sympy,Sumith1896/sympy,sunny94/temp,cswiercz/sympy,ahhda/sympy,abloomston/sympy,iamutkarshtiwari/sympy,oliverlee/sympy,sampadsaha5/sympy,meghana1995/sympy,postvakje/sympy,abhiii5459/sympy,drufat/sympy,kaichogami/sympy,kmacinnis/sympy,wanglongqi/sympy,saurabhjn76/sympy,madan96/sympy,meghana1995/sympy,emon10005/sympy,garvitr/sympy,bukzor/sympy,kaichogami/sympy,kmacinnis/sympy,souravsingh/sympy,dqnykamp/sympy,pandeyadarsh/sympy,kevalds51/sympy,Davidjohnwilson/sympy,pandeyadarsh/sympy,yukoba/sympy,cswiercz/sympy,farhaanbukhsh/sympy,aktech/sympy,farhaanbukhsh/sympy,wyom/sympy,Designist/sympy,moble/sympy,lindsayad/sympy,sahilshekhawat/sympy,jerli/sympy,atsao72/sympy,srjoglekar246/sympy,wanglongqi/sympy,toolforger/sympy,atreyv/sympy,oliverlee/sympy,asm666/sympy,VaibhavAgarwalVA/sympy,Shaswat27/sympy,debugger22/sympy,sampadsaha5/sympy,rahuldan/sympy,kaushik94/sympy,beni55/sympy,souravsingh/sympy,yukoba/sympy,toolforger/sympy,VaibhavAgarwalVA/sympy,postvakje/sympy,kaushik94/sympy,Mitchkoens/sympy,kaichogami/sympy,chaffra/sympy,aktech/sympy,moble/sympy,Arafatk/sympy,Designist/sympy,Vishluck/sympy,oliverlee/sympy,lidavidm/sympy,garvitr/sympy,amitjamadagni/sympy,jerli/sympy,kaushik94/sympy,rahuldan/sympy,grevutiu-gabriel/sympy,jamesblunt/sympy,Curious72/sympy,AkademieOlympia/sympy,ahhda/sympy,aktech/sympy,beni55/sympy,shipci/sympy,sahilshekhawat/sympy,chaffra/sympy,saurabhjn76/sympy,Titan-C/sympy,shipci/sympy,yashsharan/sympy,mafiya69/sympy,ChristinaZografou/sympy,kumarkrishna/sympy,postvakje/sympy,jaimahajan1997/sympy,mcdaniel67/sympy,shikil/sympy,shipci/sympy,emon10005/sympy,MridulS/sympy,maniteja123/sympy,abloomston/sympy,ahhda/sympy,sahmed95/sympy,ga7g08/sympy,liangjiaxing/sympy,Gadal/sympy,toolforger/sympy,vipulroxx/sympy,skidzo/sympy,jerli/sympy,wyom/sympy,Davidjohnwilson/sympy,sahmed95/sympy,grevutiu-gabriel/sympy,Gadal/sympy,AunShiLord/sympy,AunShiLord/sympy,liangjiaxing/sympy,sahmed95/sympy,Mitchkoens/sympy,AunShiLord/sympy,jaimahajan1997/sympy,rahuldan/sympy,iamutkarshtiwari/sympy,souravsingh/sympy,yashsharan/sympy,jbbskinny/sympy,wanglongqi/sympy,ChristinaZografou/sympy,lidavidm/sympy,cccfran/sympy,kumarkrishna/sympy,abhiii5459/sympy,jamesblunt/sympy,sunny94/temp,flacjacket/sympy,Shaswat27/sympy,kevalds51/sympy,ChristinaZografou/sympy,mcdaniel67/sympy,hrashk/sympy,hargup/sympy,ga7g08/sympy,vipulroxx/sympy,vipulroxx/sympy,jbbskinny/sympy,hrashk/sympy,wyom/sympy,hargup/sympy,emon10005/sympy,maniteja123/sympy,beni55/sympy,AkademieOlympia/sympy,cccfran/sympy,dqnykamp/sympy,Designist/sympy,lidavidm/sympy,MridulS/sympy,MridulS/sympy,mafiya69/sympy,Arafatk/sympy,pbrady/sympy,MechCoder/sympy,Arafatk/sympy,jaimahajan1997/sympy,Vishluck/sympy,pandeyadarsh/sympy,dqnykamp/sympy,pbrady/sympy,yashsharan/sympy,drufat/sympy,Titan-C/sympy,VaibhavAgarwalVA/sympy,Gadal/sympy,atsao72/sympy,Sumith1896/sympy,shikil/sympy,cccfran/sympy,Shaswat27/sympy,abloomston/sympy,jbbskinny/sympy,lindsayad/sympy,bukzor/sympy,chaffra/sympy,Davidjohnwilson/sympy,farhaanbukhsh/sympy,asm666/sympy,atreyv/sympy,drufat/sympy,Sumith1896/sympy,lindsayad/sympy,mafiya69/sympy,iamutkarshtiwari/sympy,skirpichev/omg,meghana1995/sympy,kevalds51/sympy,debugger22/sympy,madan96/sympy,Curious72/sympy,sampadsaha5/sympy,garvitr/sympy,kumarkrishna/sympy,Titan-C/sympy,sahilshekhawat/sympy,atreyv/sympy,hrashk/sympy,ga7g08/sympy,pbrady/sympy,Mitchkoens/sympy,skidzo/sympy,yukoba/sympy,kmacinnis/sympy,bukzor/sympy,hargup/sympy,diofant/diofant,AkademieOlympia/sympy,abhiii5459/sympy,maniteja123/sympy,jamesblunt/sympy,shikil/sympy,moble/sympy,amitjamadagni/sympy,sunny94/temp