v0.0.0.9007

New features

• New parameter pca: set this to a positive integer to reduce matrix of
  data frames to that number of columns using PCA. Only works if
  metric = "euclidean". If you have > 100 columns, this can substantially
  improve the speed of the nearest neighbor search. t-SNE implementations often
  set this value to 50.

Bug fixes and minor improvements

• Laplacian Eigenmap initialization convergence failure is now correctly
  detected.
• C++ code was over-writing data passed from R as a function argument.