import error in dataviz tutorial

I setup my system exactly as described in the tutorial website. But, I still got an import error while running the dataviz code:

```
>> python graph.py

RuntimeError: module compiled against API version a but this version of numpy is 9
Traceback (most recent call last):
File "graph.py", line 14, in
import matplotlib.pyplot as plt
File "/home/anmol/Envs/DataVizProj/local/lib/python2.7/site-packages/matplotlib/pyplot.py", line 27, in
import matplotlib.colorbar
File "/home/anmol/Envs/DataVizProj/local/lib/python2.7/site-packages/matplotlib/colorbar.py", line 32, in
import matplotlib.artist as martist
File "/home/anmol/Envs/DataVizProj/local/lib/python2.7/site-packages/matplotlib/artist.py", line 12, in
from .transforms import Bbox, IdentityTransform, TransformedBbox, \
File "/home/anmol/Envs/DataVizProj/local/lib/python2.7/site-packages/matplotlib/transforms.py", line 39, in
from matplotlib._path import (affine_transform, count_bboxes_overlapping_bbox,
ImportError: numpy.core.multiarray failed to import
```

List of packages installed in the virtualenv:

```
>> pip freeze

funcsigs==0.4
geojson==1.0.6
matplotlib==1.4.2
mock==1.3.0
nose==1.3.7
numpy==1.9.1
pbr==1.8.1
pyparsing==2.0.7
python-dateutil==2.4.2
pytz==2015.7
six==1.10.0
```

[Here](http://imgur.com/GRMzoVa) is a screenshot showing the error.

This was solved by executing `pip install -U numpy` as suggested by [this link](http://stackoverflow.com/questions/20518632/importerror-numpy-core-multiarray-failed-to-import).

My system specifications:
- Ubuntu 14.04
- Python 2.7.6