ENH: numexpr on boolean frames

simple usage of using numexpr on boolean type frame comparison

```
name                                                                    
indexing_dataframe_boolean                 13.3200   125.3521     0.1063
frame_mult                                 21.7157    36.6353     0.5928
frame_add                                  22.0432    36.5021     0.6039
frame_multi_and                           385.4241   407.4359     0.9460
```

- optional use of numexpr (though out to suggest it highly)
- example usage, many more cases like this

_frame_multi_and is the case we are talking about below, a boolean express anded with another,
can only optimize each sub-expression, and not the 3 terms together_

original issue is #724

here some runs (on travis ci), for these 4 routines
- with no numexpr (no_ne)
- with numexpr single threaded (_st)
- with numexpr (no suffix)

So numexpr helps in boolean case with and w/o parallelization
add/multiply the parallelization helps (and just numexpr doesn't do much)

```
frame_mult                              :    27.0671 [ms]
frame_mult_st                           :    85.1929 [ms]
frame_mult_no_ne                        :    86.2602 [ms]
frame_add                               :    26.3325 [ms]
frame_add_st                            :    74.8805 [ms]
frame_add_no_ne                         :    73.9357 [ms]
indexing_dataframe_boolean              :    15.0413 [ms]
indexing_dataframe_boolean_st           :    25.8873 [ms]
indexing_dataframe_boolean_no_ne        :   288.4722 [ms]
frame_multi_and                         :   637.8641 [ms]
frame_multi_and_st                      :   675.7760 [ms]
frame_multi_and_no_ne                   :   589.3791 [ms]
```