Fix mistake in ECSV reader docstring and make example testable - #5450

KeyError                                  Traceback (most recent call last)
<ipython-input-11-8cfe8b05e3da> in <module>()
      9 004 3
     10 """
---> 11 Table.read(ecsv_content, format='ascii.ecsv')

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/table/table.py in read(cls, *args, **kwargs)
   2333         passed through to the underlying data reader (e.g. `~astropy.io.ascii.read`).
   2334         """
-> 2335         return io_registry.read(cls, *args, **kwargs)
   2336 
   2337     def write(self, *args, **kwargs):

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/io/registry.py in read(cls, *args, **kwargs)
    466 
    467         reader = get_reader(format, cls)
--> 468         data = reader(*args, **kwargs)
    469 
    470         if not isinstance(data, cls):

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/io/ascii/connect.py in io_read(format, filename, **kwargs)
     35     from .ui import read
     36     format = re.sub(r'^ascii\.', '', format)
---> 37     return read(filename, format=format, **kwargs)
     38 
     39 

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/io/ascii/ui.py in read(table, guess, **kwargs)
    339                                              ' with fast (no guessing)'})
    340         else:
--> 341             dat = reader.read(table)
    342             _read_trace.append({'kwargs': new_kwargs,
    343                                 'status': 'Success with specified Reader class '

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/io/ascii/core.py in read(self, table)
   1151 
   1152         # Get the table column definitions
-> 1153         self.header.get_cols(self.lines)
   1154 
   1155         # Make sure columns are valid

/Users/deil/Library/Python/3.5/lib/python/site-packages/astropy-1.3.dev16202-py3.5-macosx-10.12-x86_64.egg/astropy/io/ascii/ecsv.py in get_cols(self, lines)
    143                 if attr in header_cols[col.name]:
    144                     setattr(col, attr, header_cols[col.name][attr])
--> 145             col.dtype = header_cols[col.name]['datatype']
    146             # ECSV "string" means numpy dtype.kind == 'U' AKA str in Python 3
    147             if not six.PY2 and col.dtype == 'string':

KeyError: 'datatype'

# - {name: a, unit: m / s, type: int64, format: '%03d'}