Update NuGet packages on OSx
Update NuGet packages on OSx

On OSx, if you don't update the package dependencies before building the project, it will fail with errors like:

```
The type or namespace nameNewtonsoft' could not be found. Are you missing an assembly reference?
```

This explains how to solve it and adds it to the Readme so others don't run into the same issue.
young-zhang/Lean,andrewhart098/Lean,StefanoRaggi/Lean,JKarathiya/Lean,Phoenix1271/Lean,AnshulYADAV007/Lean,QuantConnect/Lean,AlexCatarino/Lean,Jay-Jay-D/LeanSTP,mabeale/Lean,squideyes/Lean,JKarathiya/Lean,dpavlenkov/Lean,jameschch/Lean,kaffeebrauer/Lean,andrewhart098/Lean,tomhunter-gh/Lean,kaffeebrauer/Lean,dpavlenkov/Lean,redmeros/Lean,FrancisGauthier/Lean,dpavlenkov/Lean,young-zhang/Lean,mabeale/Lean,Phoenix1271/Lean,tomhunter-gh/Lean,mabeale/Lean,jameschch/Lean,devalkeralia/Lean,QuantConnect/Lean,jameschch/Lean,squideyes/Lean,QuantConnect/Lean,Mendelone/forex_trading,redmeros/Lean,QuantConnect/Lean,FrancisGauthier/Lean,StefanoRaggi/Lean,devalkeralia/Lean,Phoenix1271/Lean,JKarathiya/Lean,AnObfuscator/Lean,redmeros/Lean,Jay-Jay-D/LeanSTP,bizcad/Lean,andrewhart098/Lean,dpavlenkov/Lean,kaffeebrauer/Lean,kaffeebrauer/Lean,bizcad/Lean,AnshulYADAV007/Lean,Obawoba/Lean,AnObfuscator/Lean,Jay-Jay-D/LeanSTP,AnObfuscator/Lean,Mendelone/forex_trading,Obawoba/Lean,bizcad/Lean,AnshulYADAV007/Lean,squideyes/Lean,jameschch/Lean,Mendelone/forex_trading,AlexCatarino/Lean,bizcad/Lean,FrancisGauthier/Lean,tomhunter-gh/Lean,jameschch/Lean,tomhunter-gh/Lean,JKarathiya/Lean,FrancisGauthier/Lean,andrewhart098/Lean,Jay-Jay-D/LeanSTP,young-zhang/Lean,AlexCatarino/Lean,Phoenix1271/Lean,Jay-Jay-D/LeanSTP,AnshulYADAV007/Lean,Obawoba/Lean,AnObfuscator/Lean,StefanoRaggi/Lean,devalkeralia/Lean,StefanoRaggi/Lean,young-zhang/Lean,Obawoba/Lean,Mendelone/forex_trading,squideyes/Lean,redmeros/Lean,kaffeebrauer/Lean,AlexCatarino/Lean,AnshulYADAV007/Lean,mabeale/Lean,devalkeralia/Lean,StefanoRaggi/Lean