Add support for tracking Talks and Speakers at a given event

[destos]

This includes making a generic Speaker model that can be associated to many talks.
Speakers should probably have social network meta data associated with it if people are interested in contacting that user.
Speakers themselves can maybe be allowed to enter their own social information or add a bio.
Social information could be made generic enough that we support multiple and expanding lists of social networks.

[destos]

Currently models for this feature reside at: https://github.com/tulsawebdevs/tulsawebdevs.org/blob/master/talks/models.py