Merge pull request #4 from paliwalashish/master

Added docs and moved inline strings to constants
Have KMeans bail out with a warning if the number of centers found is less than the number requested
For kassign, re-use the center ids from the centers file, don't use 0:(n-1) unless no center ids are specified
Add support for multithreaded clustering to the kmeans command
Add a much richer set of sampling tools to the command line
Un-tab pom files
Initial HCatalog WIP
merged from master