text: Title: Should we port bottleneck to C?
  Body: I'm trying to port nansum to C (without using cython) to get a feel for how bottleneck would look written in pure C.
  
  What I have so far (in the c_rewrite branch) is a nansum with reduced features that compiles but does not work at all. I have not yet tried to deal with reference counting because I don't yet know how. Any help, comments, appreciated.
  
  Here's a demo on how to compile:
  
  ```
  /bottleneck/bottleneck/template (c_rewrite)$ python setup.py build_ext --inplace
  running build_ext
  building 'nansum' extension
  <snip>
  In [1]: from nansum import nansum
  In [2]: a=np.random.rand(4)
  In [3]: nansum(a)
  ---------------------------------------------------------------------------
  SystemError                               Traceback (most recent call last)
  <ipython-input-3-1d96a990bfd9> in <module>()
  ----> 1 nansum(a)
  
  SystemError: error return without exception set
  ```
  