Pandas-td

* Set minimum requests version to 2.21.0 (9)

* Tweaked dependency versions (7, 8)

* New magic function %td_job.
* New option --timezone (-T) for magic query functions.
* New option --connection (-c) for magic query functions.
* Deprecated option --engine (-e) for magic query functions.
* (Experimental) New function ``create_queue`` for background job execution.
* (Experimental) New option --queue (-a) for magic query functions.
* Support HipChat and Slack as notification channel for background jobs.

* Several bug fixes of to_td().

* to_td() now waits until imported data becomes visible. It also prints progress in HTML.
* New option --engine (-e) for magic query functions.

* New function ``read_td_job``.