dispatch_to_series is very slow
Since pandas 0.24.0   I found there is a function in ops.py named dispatch_to_series.
But dispatch_to_series is very slow,  that makes my code slower.
when I use pandas==0.23.0, it cost about 100 seconds,  but  when I use pandas==0.24.*  It cost 583 seconds.

This is my profile result.
![factor_test_1555059433](https://user-images.githubusercontent.com/22519984/56031324-b6ac7380-5d51-11e9-853d-8dcdf7b16417.png)
A and I found pandas become more slower because you call isinstance function too many times
link to history merge : [[PERF] use numexpr in dispatch_to_series #22284](https://github.com/pandas-dev/pandas/pull/22284)