isympy: hook in-tree sympy into python path if running in-tree version of isympy
isympy: hook in-tree sympy into python path if running in-tree version of isympy

fix-for: #436

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