Deprecation warning for SparseDataFrame shown for repr / every operation
If you are still using the SparseDataFrame class, the warnings are quite sticky:

```python
In [5]: sparse_df = pd.SparseDataFrame(np.array([[1,2, np.nan], [np.nan, 5, 6]]), columns=['a','b','c'])
/home/joris/miniconda3/envs/dev37/bin/ipython:1: FutureWarning: SparseDataFrame is deprecated and will be removed in a future version.
Use a regular DataFrame whose columns are SparseArrays instead.

See http://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating for more.

  #!/home/joris/miniconda3/envs/dev37/bin/python

In [6]: sparse_df                                      
Out[6]: /home/joris/scipy/pandas/pandas/core/frame.py:3337: FutureWarning: SparseSeries is deprecated and will be removed in a future version.
Use a Series with sparse values instead.

    >>> series = pd.Series(pd.SparseArray(...))

See http://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating for more.

  return klass(values, index=self.index, name=items, fastpath=True)

     a    b    c
0  1.0  2.0  NaN
1  NaN  5.0  6.0

In [7]: sparse_df + 1                               
/home/joris/scipy/pandas/pandas/core/frame.py:3337: FutureWarning: SparseSeries is deprecated and will be removed in a future version.
Use a Series with sparse values instead.

    >>> series = pd.Series(pd.SparseArray(...))

See http://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating for more.

  return klass(values, index=self.index, name=items, fastpath=True)
/home/joris/scipy/pandas/pandas/core/ops.py:2304: FutureWarning: SparseSeries is deprecated and will be removed in a future version.
Use a Series with sparse values instead.

    >>> series = pd.Series(pd.SparseArray(...))

See http://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating for more.

  name=self.name)
/home/joris/scipy/pandas/pandas/core/sparse/frame.py:298: FutureWarning: SparseDataFrame is deprecated and will be removed in a future version.
Use a regular DataFrame whose columns are SparseArrays instead.

See http://pandas.pydata.org/pandas-docs/stable/user_guide/sparse.html#migrating for more.

  default_fill_value=self.default_fill_value).__finalize__(self)
Out[7]: 
     a    b    c
0  2.0  3.0  NaN
1  NaN  6.0  7.0
```

So they are also raised each time you display them (repr), on each operation (like the addition I did).

I know users can filter them, but ideally they would be shown a bit less I think to not annoy users too much.

cc @TomAugspurger 