update doc ingest data

char error (bad commit)

we support python 3.x

IEX now charging for the service. Yahoo restored theirs. going back

to Yahoo Finance. IEX stopped the free service and started the
IEX Cloud service which needs an API key and the free tier is not
enough for to keep using it.

bugfix: can't access attr _execution_id if doesn't exist

bugfix: execution id definition is missing

use the stop callback only per execution and not one for all

that's just simpler

bugfix: callback were not initialized

Merge pull request #8 from shlomikushchi/test_perf_tracker

Test perf tracker