RcppEigen Submatrix Views

[MRTGENC]

It seems that Eigen 3.4.90 supports submatrix views (slicing, indexing and block operations).
The lack of this feature in RcppEigen makes it difficult to work with RcppEigen.
It would be good to include this features in the RcppEigen package.

[eddelbuettel]

Please take a look at #103 -- we are still trying to get to 3.4.0.

[MRTGENC]

Thank you.
I'm looking forward to it.