Update 2018-04-06-AvaTax-18-4-patch-notes.md
Update 2018-04-06-AvaTax-18-4-patch-notes.md

typos and updates
bob-erdman/developer-dot,ted-spence-avalara/developer-dot,ted-spence-avalara/developer-dot,bob-erdman/developer-dot,ted-spence-avalara/developer-dot,ted-spence-avalara/developer-dot,bob-erdman/developer-dot,ted-spence-avalara/developer-dot,bob-erdman/developer-dot,bob-erdman/developer-dot