Change workshop and conference date

[jenlgray]

"A full day of PhoneGap, web, and mobile dev talks on Oct. 11th, plus an optional full day of workshops on Oct. 12th"

And change Oct 11 & 12 2017 • NYC to Oct 11 (conference) & 12 (workshops)

[GarthDB]

A couple more places to change the date:

• the twitter card
• the smaller logo

[GarthDB]

It's fine to change these to just say oct 11, 12 or 11 & 12. Just so it's accurate; people can visit the site the get the break down of the days.