REF Move get_all_tickers_traded() to internals.
REF Move get_all_tickers_traded() to internals.

Since it depends on our internal DB layout it should live in internals.py.

YihaoLu/pyfolio,raybuhr/pyfolio,quantopian/pyfolio,femtotrader/pyfolio,sketchytechky/pyfolio,dursk/pyfolio,ChinaQuants/pyfolio,femtotrader/pyfolio,yanheven/pyfolio,r0k3/pyfolio,YihaoLu/pyfolio,sketchytechky/pyfolio,dursk/pyfolio,ChinaQuants/pyfolio,raybuhr/pyfolio,r0k3/pyfolio,chayapan/pyfolio,quantopian/pyfolio,yanheven/pyfolio