CParser raises ZeroDivisionError on empty file
Just updated to pydata/pandas@master and now have a failing test:

``` python
======================================================================
ERROR: test_raise_on_no_columns (pandas.io.tests.test_parsers.TestCParserLowMemory)
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Traceback (most recent call last):
  File "/.../pandas/pandas/io/tests/test_parsers.py", line 2337, in test_raise_on_no_columns
    self.assertRaises(ValueError, self.read_csv, StringIO(data))
  File "/usr/local/Cellar/python/2.7.3/Frameworks/Python.framework/Versions/2.7/lib/python2.7/unittest/case.py", line 471, in assertRaises
    callableObj(*args, **kwargs)
  File "/.../pandas/pandas/io/tests/test_parsers.py", line 2026, in read_csv
    return read_csv(*args, **kwds)
  File "/.../pandas/pandas/io/parsers.py", line 396, in parser_f
    return _read(filepath_or_buffer, kwds)
  File "/.../pandas/pandas/io/parsers.py", line 194, in _read
    parser = TextFileReader(filepath_or_buffer, **kwds)
  File "/.../pandas/pandas/io/parsers.py", line 475, in __init__
    self._make_engine(self.engine)
  File "/.../pandas/pandas/io/parsers.py", line 582, in _make_engine
    self._engine = CParserWrapper(self.f, **self.options)
  File "/.../pandas/pandas/io/parsers.py", line 953, in __init__
    self._reader = _parser.TextReader(src, **kwds)
  File "parser.pyx", line 480, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:4508)
ZeroDivisionError: integer division or modulo by zero

----------------------------------------------------------------------
```

ff5797959ef5d78682d6e85d97356407f9d63de6 creates the problem (though I'm not sure if that test existed before that commit).  Thoughts on what's going on?
