Sketch sparsify operation (untested)
Implement tare operation (still broken)
Implement sparsify_rows (still broken)
Merge branch 'sparse-value' into sparsify
Split sparsify.hpp into differ.hpp + differ.cc
Add runner + benchmark bindings to sparsify + tare
Merge branch 'sparse-value' into sparsify
Implement Differ::absolute_to_relative and relative_to_absolute
Fix assertion in absolute_to_relative
Refactor differ; add loom.tare_ field
Merge branch 'master' into sparsify
Fix schema to use new normalized_*() functions
Rename typedef Value to ProductValue in most places
Get sparsify tests to pass
Merge pull request #28 from priorknowledge/query-server

Query server
Clean up differ.cc
Merge branch 'master' into sparsify
Fix benchmarking test
Support sparse real values that are mostly-zero
Add tare & sparsify to test_happy_path