Update Travis mono version
Update Travis mono version

StefanoRaggi/Lean,JKarathiya/Lean,jameschch/Lean,jameschch/Lean,QuantConnect/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,jameschch/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,QuantConnect/Lean,JKarathiya/Lean,AlexCatarino/Lean,jameschch/Lean,jameschch/Lean,StefanoRaggi/Lean,JKarathiya/Lean,QuantConnect/Lean,QuantConnect/Lean,AlexCatarino/Lean,JKarathiya/Lean,StefanoRaggi/Lean