MAINT: Numpy deprecated boolean unary '-' operator
I'm sure there are more of these, but I just caught this one when I was raising on all warnings.

ahh..prob a fair number of these....
 Might be trivial to write a log only on this deprecation warning to wrap the test suite in. I have no idea though.  
 this is under numpy 1.9-dev right?
 Yeah `1.9.0.dev-3e61f86`
 we test with numpy master in every build: https://travis-ci.org/jreback/pandas/jobs/23688029

is their a way to make nose print out the warnings (i'll have to turn off the deprecation stuff) because we hide that (or maybe that's all I need to do?)
 Deprecation warnings are filtered in python by default. I'm not really sure how to show them using nosetest. This is the code to show them

```
import warnings
warnings.simplefilter('always', DeprecationWarning)
```

But I'm not sure how to get nosetest to respect that. Maybe you could put it in `.pystartup`. Or put it at the beginning of a `pandas.test()` function, but I don't think pandas test suite can be run that way.
 I had a filter to 'error', because I wanted to debug another warning I had, but my code raised on this first.
 ok...easy enough...to run it and look for these
 going to close in favor of #6960 their are like a ton (think I got them though)
 @jseabold this turned into a project!

numpy really turned on the spigot with depr warnings! (of course the conversions that we were doing were a bit suspect anyhow)..

e.g. you can't compare `np.datetime('NaT')` with `tslib.NaT` (e.g. its a datetime64 cmp with an integer (but `np.datetime('NaT').astype('int64') == tslib.NaT` works just fine)
