Problems with Basemap.scatter

Nadie ha tomado este issue todavía.

Hi,

I have stumbled over a bug in scatter plot. With latlon=True, it crashes with zero, one or two points.

Example code:

``` python
import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap

bmap = Basemap(projection='merc',
llcrnrlon=9, urcrnrlon=13,
llcrnrlat=63, urcrnrlat=65,
resolution='c')

lon = [10.0, 12.0]
lat = [64.0, 65.0]

bmap.scatter(lon, lat, latlon=True)

plt.show()
```

This crashes with the following Traceback:

```
Traceback (most recent call last):
File "a.py", line 12, in
bmap.scatter(lon, lat, latlon=True)
File "/opt/anaconda/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.py", line 536, in with_transform
x = self.shiftdata(x)
File "/opt/anaconda/lib/python2.7/site-packages/mpl_toolkits/basemap/__init__.py", line 4775, in shiftdata
thresh = 360.-londiff_sort[-2]
IndexError: index -2 is out of bounds for axis 0 with size 1
```

I am using python 2.7.10, matplotlib 1.4.3, basemap 1.0.7 on a 64-bit Linux machine

Comienza ejecutando el ejemplo proporcionado de Basemap.scatter con latlon=True e inspecciona el punto de entrada shiftdata en mpl_toolkits/basemap/__init__.py, donde el traceback falla para entradas pequeñas. Se considera terminado cuando scatter maneja cero, uno y dos puntos sin generar IndexError.

Escrito por el modelo de indexación a partir del texto del issue.