No output of xticklabels when plotting to gridspec subplots
What seems to be the problem here?
The xticklabels for the first axes defined in a gridspec are not visible when plotting with pandas. The corresponding plot using pyplot.plot does have the labels. 

pandas 0.16
matplotlib 1.4.3

``` python
import pandas as pd
import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt

%matplotlib inline
df = pd.DataFrame(np.random.randn(8, 4), index=np.arange(8), columns=['A', 'B', 'C', 'D'])
```

Matplotlib

``` python
gs = mpl.gridspec.GridSpec(2, 4)
ax1 = plt.subplot(gs[0,:-1])
ax2 = plt.subplot(gs[0,-1])
ax3 = plt.subplot(gs[1,:-2])
ax4 = plt.subplot(gs[1,-2:])

ax1.plot(df.index.values, df.A)
ax2.plot(df.index.values, df.B)
ax3.plot(df.index.values, df.C)
ax4.plot(df.index.values, df.D)

gs.tight_layout(plt.gcf())
```

![mpl](https://cloud.githubusercontent.com/assets/7450204/7680755/08db0c76-fd6a-11e4-9632-d7a0bfca594f.png)

pandas

``` python
gs = mpl.gridspec.GridSpec(2, 4)
ax1 = plt.subplot(gs[0,:-1])
ax2 = plt.subplot(gs[0,-1])
ax3 = plt.subplot(gs[1,:-2])
ax4 = plt.subplot(gs[1,-2:])

df.A.plot(ax=ax1)
df.B.plot(ax=ax2)
df.C.plot(ax=ax3)
df.D.plot(ax=ax4)

gs.tight_layout(plt.gcf())
```

![pandas](https://cloud.githubusercontent.com/assets/7450204/7680770/205d661e-fd6a-11e4-8d2d-2629e2528426.png)

It seems that xticklabels are absent when plotting with pandas to the first axis generated in a gridspec. Switching ax1 and ax2 definition:

pandas

``` python
gs = mpl.gridspec.GridSpec(2, 4)
ax2 = plt.subplot(gs[0,-1])
ax1 = plt.subplot(gs[0,:-1])
ax3 = plt.subplot(gs[1,:-2])
ax4 = plt.subplot(gs[1,-2:])

df.A.plot(ax=ax1)
df.B.plot(ax=ax2)
df.C.plot(ax=ax3)
df.D.plot(ax=ax4)

gs.tight_layout(plt.gcf())
```

![pandas2](https://cloud.githubusercontent.com/assets/7450204/7680788/39b53678-fd6a-11e4-85b0-4c9b091b2354.png)

Related?
http://stackoverflow.com/questions/29552382/legend-overriding-x-label-and-x-ticks
