Clicks and Unique Clicks

Ted Seifert #255
Merge branch 'patch-3' of https://github.com/TeddySeifert/docs into TeddySeifert-patch-3
moved clicks and unique clicks to clicks.md
Updated the content
Merge branch 'TeddySeifert-patch-3' into develop
Merge branch 'develop' of https://github.com/sendgrid/docs into develop