0.2.0 - Outrageous Orange

New features

• Added fortify() method to plot metamers directly with 'ggplot2'.

• The perturbation argument in metamerize() can now be a vector of equal in
  length to change

• Multiple minimization functions can be passed to minimize.

• Added function mean_self_proximity() that computes the inverse of the mean
  minimum distance between each datapoint. Pass it to minimize if you don't want
  it to clump.

• Small speed improvement.