move xzip to utils
start looking at nearest neighbors, text and web based
save time on import
improve web interface for closest neighbors display
add a wrapper around kd tree
use scikit KDtree instead of scipy one (faster according to line_profiler)
Improve feature vectors computation speed

the biggest improvement was caching the result of parenting_cat in a
dictionnary and using a KDtree for spatial query instead of mongo.