add __iter__() for TableList to support enumerate()

[stonyw]

    tables = camelot.read_pdf(filename)
    for idx, table in enumerate(tables):   # Warining: Expected type 'Iterable[_T]', got 'TableList' instead  in pycharm
        pass

[stefan6419846]

Are you able to provide a corresponding test as well?

[foarsitter]

I agree with @stefan6419846, your provided example is almost a test-case. Whilst the improvement looks very trivial a test-case is easy to provide.

[stonyw]

I'll add tests soon.