[Do Not Merge] [Example] Add per-request logging context

[coltonlw]

This adds a custom request object which has additional attributes "id" and "logger". logger is a LoggerAdapter which adds the request id to each message string. In the future this can be expanded to include additional per-request context information with each logging call, including extra keys when we log in JSON. Also added a thread local request context which can be accessed globally via set_current_request and get_current_request

Example output:

2016-09-08 11:09:46 scitran.api base.py  105:INFO Initialized request request_id=0935954b-1473350986

Fixes: #199, #451

[coltonlw]

FYI pushed a one-line change to remove unused request_id attribute

[coltonlw]

Talking to Megan, I'm going to make a new feature branch which does not have global request context / set_current_request + get_current_request functionality. Most of the logger calls that do not already have access to the request are of level debug and so not useful in production anyway and not worth the complexity of the global request context. I'll leave this open incase anyone still wants to review the implementation for curiosity sake

[coltonlw]

Closing because the new PR will be opened from a different branch