Failure to parse docstrings where a section contains header-like content

numpydoc.docscrape.NumpyDocString in version 1.9.0 fails to parse docstrings if there is content within a section that resembles a section header, e.g. the "Parameters\n----------" contains " Parameters\n----------"

Example reproducer: a function that takes a function as an argument and returnsanother function. The following docstring explains the returned function:

def wrapper(func):
    '''
    Wrap a simple function so that it takes a message string that gets printed to stdout when invoked.

    Parameters
    ----------
    func: function
        Function to be wrapped. This can be any arbitrary synchronous function.

    Returns
    -------
    wrapped_function: function
        The returned function has the following signature::

            wrapped_function(
                message,
                *args,
                *kwargs,
            )
                \'\'\'
                Parameters
                ----------
                message: str
                A custom message to be printed when the wrapped function is called.
                *args
                    Additional arguments that are passed into the original function.
                **kwargs
                    Extra arguments to the original function.
                \'\'\'
    '''

However, when using numpydoc.docscrape.NumpyDocString to parse this docstring, for example:

parsed = NumpyDocString(<example docstring above>)

...an exception is raised claiming to have duplicate Parameters section:

ValueError: The section `Parameters` appears twice in  
Wrap a simple function so that it takes a message string that gets printed to stdout when invoked.

The desired behavior is to treat the nested Parameters "section" as regular content and not an actual section.

Start with the NumpyDocString entry point and run the provided wrapper docstring reproducer against version 1.9.0. Trace how indented header-like content is recognized while parsing sections, then add coverage showing that the nested Parameters text remains regular content and does not raise a duplicate-section error.