Add vbench job to jenkins
a vbench jobs was added to travis  (ae80d24e) 3 weeks ago, 
Today I did some more work there, added some code to make it easy
to collect all that data back into a comfy dataframe,

Although I think this was a cool hack (and although using pandas
and statsmodels to fit a model and get some confidence intervals on the results
would make it even cooler), It basically looks like the results  fluctuate too much
to make this a useful metric. The repeatability is awful, 

@changhiskhan mentioned you have a jenkins server stowed somewhere,
all the building blocks are already in place for jenkins to test commits on master
and give a reliable alert when a performance regression occurs, It might be a good
idea to set that up.

I'll leave the VBENCH build active in travis, It's a poignant dataset to use in some
future pandas tutorial ( timeseries, plotting, parsing, aligning, cleaning, etc')

You can play with the data yourself if you're interested:

``` python
In [1]: cd ~/src/pandas/vb_suite/
In [3]: from perf_HEAD import get_all_results_joined
In [4]: df=get_all_results_joined()
In [27]: df
Out[27]: 
<class 'pandas.core.frame.DataFrame'>
Index: 140 entries, append_frame_single_homogenous to write_csv_standard
Columns: 187 entries, 771 to 968
dtypes: float64(187)

In [28]: df.index[:5]
Out[28]: Index([append_frame_single_homogenous, append_frame_single_mixed, concat_series_axis1, concat_small_frames, ctor_index_array_string], dtype=object)
```

![screen](https://f.cloud.github.com/assets/1820866/15467/7c54f0de-4770-11e2-8b11-647632053fca.png)
