Add/autosend - Autosend integration

Logo: https://d1touj61nfw0sa.cloudfront.net/AutosendLogo.eps

This is a pull request to add Autosend integration into Segment.io. I provided a link to the Autosend logo above, as I could not upload a vector image to Github (they only allow gif, jpg, and png apparently)

Description: Automatically send personalized SMS, push notification, and email messages to your users based on what they do in your web or mobile app.