ERR: more informative error message on bool arith op failures
closes #7011 

can you repush, to make it rebuild travis 
 also can you update the release note with this issue as well , #6762
 maybe add to API changes as well on v0.14.0, and an example if you think its worth it 
 looks fine...

don't merge just yet...trying to fix the caching issue on master
 sure no prob
 anything i can do to help on that front?
 all see
u can merge 
 @jreback all see? don't understand...still failing i think there's some floating point exception ... let me check it ou
 meant all set when u r ready
caching fixed in master 
 hmm...can you rebase/repush...see if their error repeats
 having some trouble repro-ing this. need a bit more time to track it down ... might have to spin up an ubuntu machine
 hows this coming?
 ahhh github search was useful: turned up #3819 :)
 what's strange is that it can only be reproduced on python 3.2 modding by 0 works fine on my local python 2.7.6
 @jreback i'm okay with leaving `mod` as is for now. let me check to see if my other addition to the ops module screwed anything else up ... i don't think so but better safe than sorry
 3.2 runs numpy 1.6.2 iirc
 yep this is fine ... the `_combine_*` handle the `r*` ops that i've given `op_str`s to.
 these are also all hit in `test_arith_flex_frame`
 @jreback any last words?
 g2g
