support pandas Series as input for lat/lon -> x/y conversion

Using pd.Series() as input for lat/long -> x/y conversion does currently raise a RuntimeError:

x,y = map_katins(df["lon"], df["lat"])
RuntimeError                              Traceback (most recent call last)
<ipython-input-139-693c51387321> in <module>()
     15 #    map_katins.plot(x, y, "ro", markersize=10)
     16 x,y = map_katins(df["lon"].values, df["lat"].values)
---> 17 x,y = map_katins(df["lon"], df["lat"])
     18 map_katins.plot(x, y, "o", color="grey", markersize=5)
     19 

C:\portabel\miniconda\envs\katins\lib\site-packages\mpl_toolkits\basemap\__init__.pyc in __call__(self, x, y, inverse)
   1146             except TypeError:
   1147                 y = [_dg2rad*yy for yy in y]
-> 1148         xout,yout = self.projtran(x,y,inverse=inverse)
   1149         if self.celestial and inverse:
   1150             try:

C:\portabel\miniconda\envs\katins\lib\site-packages\mpl_toolkits\basemap\proj.pyc in __call__(self, *args, **kw)
    284             outxy = self._proj4(xy, inverse=inverse)
    285         else:
--> 286             outx,outy = self._proj4(x, y, inverse=inverse)
    287         if inverse:
    288             if self.projection in ['merc','mill','gall']:

C:\portabel\miniconda\envs\katins\lib\site-packages\mpl_toolkits\basemap\pyproj.pyc in __call__(self, *args, **kw)
    386             _proj.Proj._inv(self, inx, iny, radians=radians, errcheck=errcheck)
    387         else:
--> 388             _proj.Proj._fwd(self, inx, iny, radians=radians, errcheck=errcheck)
    389         # if inputs were lists, tuples or floats, convert back.
    390         outx = _convertback(xisfloat,xislist,xistuple,inx)

_proj.pyx in _proj.Proj._fwd (src/_proj.c:1571)()

RuntimeError: 

Using

x,y = map_katins(df["lon"].values, df["lat"].values)

works...

import mpl_toolkits.basemap
mpl_toolkits.basemap.__version__
'1.0.7'

首先，使用提供的 Basemap 1.0.7 上下文，在入口点 map_katins(df["lon"], df["lat"]) 重现该故障，并将其与正常工作的 .values 调用进行比较。跟踪转换进入 Basemap 投影调用的过程，并确定现有回归测试的位置；当 pandas Series 输入能够在没有 RuntimeError 的情况下完成转换，同时现有数组输入继续正常工作时，即表示完成。