Apply with args but only one arg gives TypeError
I can't seem to get the arguments on the apply function to work when there is only one argument. The following code reproduces my error in Pandas 0.91. It doesn't seem to recognize a single argument as a one element tupple. 

``` python
data = {'state':['Ohio','Ohio','Ohio','Nevada','Nevada'], 'year':[2000,2001,2002,2001,2002],'pop':[1.5,1.7,3.6,2.4,2.9]}
frame = pd.DataFrame(data)

def testfunc(x, *args):
    summand = args[0]
    y = x + summand
    return y

 #this works okay
frame['year'].apply(testfunc, args = (7,7))

#this does not
frame['year'].apply(testfunc, args = (7))
#TypeError: testfunc() argument after * must be a sequence, not int
```
