Scipy 1.0 Roadmap

Note: to be discussed on the list, don't merge.
Sorry, of course it's true there's no "sensible reallocation strategy" if the elements are not inserted at the end, which gives LIL quadratic scaling in the worst case:
```
>>> m_dok = scipy.sparse.dok_matrix((300000,300000))
>>> m_lil = scipy.sparse.lil_matrix((300000,300000))
>>> i, j = [0]*300000, list(range(300000))[::-1]
>>> %timeit -n1 -r1 insertion(m_dok, i, j)
1 loops, best of 1: 1.73 s per loop
>>> %timeit -n1 -r1 insertion(m_lil, i, j)
1 loops, best of 1: 58.1 s per loop
```