Implement cached scorer for entropy queries (untested)
Reimplement entropy query with cached RestrictionScorer
Implement cheaper entropy caching computation
Use matrix encoding for Query.Request.Entropy
Merge branch 'entropy-matrix' into cache-entropy-matrix

Conflicts:
	src/query_server.cc
Clean up C++ scorer and query server
Fix typing error in scorer
Avoid duplicate work in C++ entropy computation
Further optimize C++ entropy computation
Merge branch 'master' into cache-entropy-matrix

Conflicts:
	loom/preql.py
	loom/query.py
Set OMP_NUM_THREADS=2 in .travis.yml
Merge branch 'entropy-tests' into cache-entropy-matrix

Conflicts:
	loom/query.py