Fix ATLAS_label

```python
import ROOT
from rootpy.plotting import Hist
from rootpy.plotting.style import set_style
from rootpy.plotting.style.atlas.labels import ATLAS_label
from rootpy.interactive import wait

set_style('ATLAS')
hpx = Hist(100, -4, 4, name="hpx", title="This is the px distribution")
ROOT.gRandom.SetSeed()
for i in xrange(1000):
    hpx.Fill(ROOT.gRandom.Gaus())
hpx.GetXaxis().SetTitle("random variable [unit]")
hpx.GetYaxis().SetTitle("#frac{dN}{dr} [unit^{-1}]")
hpx.SetMaximum(80.)
hpx.Draw()
ATLAS_label(.4, .8)
wait()
```

![6e588b70301742c49f1fd0b6bd1dc543](https://f.cloud.github.com/assets/202816/318288/7f99eadc-9893-11e2-9f85-428964af9871.png)