added similarityUpdateSemaphore to model

incremenet similarityUpdateSemaphore in controller after recomputing similarities

renamed tooltip helper, updated template to new name

explanation of current issues in comment in tooltip helper
incremental progress on getting tooltips working right
refreshing tooltips work

need to implement KSD's dissimilar algorithm and submit pull request
make computed property similarityMatrix observable in controller init

change helper to take similarityMatrix as an argument

changed template to pass similarityMatrix to the helper
get rid of extra variable assignment in helper