[gsoc18] tensor project schedule slightly modified

For the sake of feasibility I slightly modified my project schedule.

I added an implementing stage in the 2nd project phase for the
interoperability with the matrix and vector template classes.

I removed the matrificization or vectorization in the 3rd project
phase and replaced it with an implementation stage for iterators and
the iterator concept.

I will have only one week to implement recursive tensor contraction
algorithms which is not a lot. So there might be a bottleneck. I
categorize mathematical operations more important for a tensor class
than supporting iterators. So I would like to put the emphasis on
these. If it takes longer I would like to postpone the implementation
after the gsoc project.

Are you okay with the changes made?

Cem