stable v4.0.0

Added:

• Support for Gaussian radial basis function.
• Class to construct RbfoptBlackBox from user data (rbfopt_user_black_box).
• The shape of the multiquadric and Gaussian RBF can now be set at runtime using the rbf_shape_parameter option in RbfoptSettings.
• Automatic selection of the shape parameter.
• Option max_cross_validations to limit the total number of cross validations performed.

Changed:

• Improved numerical stability for nonlinear models in Gutmann's algorithm.
• Cross validation now uses Gaussian RBFs and different values of the shape parameter.
• BlackBox renamed to RbfoptBlackBox.
• RbfoptBlackBox interface now requires returning var_type instead of a list of integer vars.
• RbfoptBlackBox.evaluate_fast is now called evaluate_noisy, and requires returning an estimate of the error.
• Documentation and examples are now distributed within the rbfopt module.
• README updated with new installation instructions and minimal examples.

Removed:

• Module rbfopt_config is no longer necessary.