Table unpickling fails

To reproduce, follow the first example in the `astropy.table` docs, then pickle and unpickle the table:

    from astropy.table import Table
    from astropy.io.misc import fnpickle, fnunpickle

    a = [1, 4, 5]
    b = [2.0, 5.0, 8.2]
    c = ['x', 'y', 'z']
    t = Table([a, b, c], names=('a', 'b', 'c'))

    fnpickle(t, 'test.pik')
    t = fnunpickle('test.pik')

With cPickle, I get an `AttributeError: 'Column' object has no attribute '_units'`. 

With pickle I get `AttributeError: 'list' object has no attribute 'name'`.

Hope this isn't an issue in 0.2...