aded negative integer division
Merge https://github.com/adambard/learnxinyminutes-docs
aded negative integer division same as in python3
comment about floats in integer division
Merge https://github.com/adambard/learnxinyminutes-docs

Added two minor changes in integer division to make it clear
Merge pull request #709 from NadOby/master

example of negative integer division