ENH: numexpr on boolean frames

simple usage of using numexpr on boolean type frame comparison

```df > df2``` (where indexed the same)

offers pretty good speedups (10x), df is 100,000 x 100

indexing_dataframe_boolean                 12.7871ms   125.3111ms     0.1020


- optional use of numexpr (though out to suggest it highly)
- example usage, many more cases like this

original issue is #704