Fixed Suggests to stay on CRAN

Fixed Suggests issue to get back on CRAN. Packages in Suggests were moved
to Depends, removed, or protected by requireNamespace.

Accepted to CRAN on 9/26/24.

GauPro 0.2.12

Fixed CRAN warning.

Added k_xyz(...) alias for kernels (replaces xyz$new(...))

Accepted to CRAN on 6/10/24.

Fixed test error

Fixed unreliable test to keep it on CRAN (again).

Very minor update

GauPro 0.2.8

Fixed unreliable test to keep it on CRAN.

Accepted to CRAN on 2/27/23.

Back on CRAN

Improved summary, importance, plots.

Added gradpredvar, AugmentedEI, CorrectedEI, optimize_fn.

GauPro was removed from CRAN on 1/25/23, this puts it back on CRAN.
Accepted to CRAN on 2/12/23.

Minor improvements

GP kernel model maxEI can now be run using mixopt to account for discrete
inputs.

Improved GP kernel model workability when input is formula and data frame.

Added importance for kernel model, greatly improved summary.

Fixed error in tests to prevent being removed from CRAN.

Accepted to CRAN on 11/24/22.

Back on CRAN

Added kernels for factors.

Changed default number of restarts to zero, and added checking more starting
points. Should make it faster.

Can give in data as data and formula instead of matrix and vector.

Package was removed from CRAN on 10/3/22. This fixes the issue.

Accepted to CRAN on 11/14/22.

Fixed CRAN error

Fixed examples to eliminate CRAN errors.

Minor updates

Minor update to kernels

Minor fixes again

Finally fixed Rcpp error that showed up on Valgrind. Published to CRAN 9/11/2017.