0.9.0 CRAN release with vignette fixes

This is a patch for a vignette that has occassional building problems, and the last release before the major release 1.0 with a long-form publication.

Please take a look at the iotables: an r Package for Reproducible Input-Output Economics Analysis, Economic and Environmental Impact Assessment with Empirical Data manuscript to describe in more detail for a journal submission the methodology and further development philosophy of iotables.