added notes and warnings

Copied from substitution tags page and modified to fit section tags
Create Google.md

creating partner page for Google. More partner pages to come soon
Moved comment about html tags

This comment about HTML tags was found on the SMTP API Overview and not in context on the page where it makes the most sense to have this message.
Cleaned up Web API Overview

There's no need for mention of our API Workshop since it doesn't exist any longer. Also, this could be confused with the Code Workshop
Updated headers for responses to make response codes, Errors and Success all h3s
Added an example URL 
Added example URL with user/pass params
In depth explanation of nesting

I was originally confused by the statement "Section tags are an extension of substitution tags". I assumed that this meant "it works the same way" rather than "you must nest sections tags in substitution tags". These changes are added in order to attempt to clear up this confusion by changing the wording around and adding very specific substitution value tables to show what was replaced, how, and when by the API.
Updated link to Greplin Tornado library

Closes #597
Merge branch 'pr/600' into develop
Merge remote-tracking branch 'origin/pr/599' into develop
Merge remote-tracking branch 'origin/pr/596' into develop
Merge remote-tracking branch 'origin/pr/595' into develop
Merge remote-tracking branch 'origin/pr/590' into develop
merge pr/578