v0.5.3

• Changed to a new way of splitting the tree when building it.
  The sub tree split is made so that each leaf node will have exactly leaf_size points in it (except the last). The last node will have n_points % leaf_size points in it and it will always be the node with the highest index. In each recursive step we calculate if the last node will happen on the left or right side of the current sub tree. If the last node will be found in the left side of the sub tree we split the tree such that the right side will be a complete binary tree and vice versa.
• Default leaf_size changed to 5
  From my benchmarks it seems that 5 is a good number (for euclidian distance). Different distances that are more or less heavy to compute is likely to change this (the heavier the smaller leaf_size).
• Removed manually inlining distance function
  If we later want to support different measures than it is unfeasible to inline the distance function explicitly. Using a separate function and the @inline macro (in 0.4) does not seem to have a performance hit compared to manually inlining.