Don't include Eigen stdvector fix until it is required.

Signed-off-by: Steven Lovegrove <stevenlovegrove@gmail.com>
Updated assignment operator to handle cross type assignment correctly (e.g. maps).

Signed-off-by: Steven Lovegrove <stevenlovegrove@gmail.com>
Merge pull request #4 from stevenlovegrove/CRTP-update

Crtp update