Self maps only work when H*(X) is generated by one element as a Steenrod module

[dalcde]

No description provided.

[hoodmane]

This is closely related to #27. In general, if we are computing Ext(M, N), we have actions of Ext(M, M) and Ext(N, N). If we only compute Ext with second variable k, then we can compute the action of Ext(k, k) on Ext(M, k) but we don't really know what Ext(M, M) is so it's a bit of a trick to make it act on Ext(M, k).