BUG: data frame plot hangs when logx True and some x are zero
```
In [1]: import pandas as pd
In [2]: import matplotlib.pyplot as plt
In [3]: import numpy as np
In [8]: pandas.version.version 
Out[8]: '0.14.1'
In [9]: x = [1,0]
In [10]: y= [2,3]
In [11]: df = pd.DataFrame()
In [12]: df['x'] = x
In [13]: df['y'] = y
In [14]: df
Out[14]: 
   x  y
0  1  2
1  0  3
In [15]: df.plot('x', 'y', kind = 'scatter')
Out[15]: <matplotlib.axes.AxesSubplot at 0x10d366590>
In [16]: plt.show() # this works
In [17]: df.plot('x', 'y', logx = True, kind = 'scatter')
Out[17]: <matplotlib.axes.AxesSubplot at 0x10d39bf10>
In [18]: plt.show() # hangs forever
```
