Add guava's (Google library) consistent hashing function.
Review fixes for digest-guava
Moving guava from src/lib/guava to src/lib/salad
Merge branch 'stable'

Conflicts:
	src/box/CMakeLists.txt
	src/ffisyms.cc
	src/lib/CMakeLists.txt
	src/lib/salad/CMakeLists.txt
	src/lua/digest.lua
	test/box/digest.test
	test/unit/CMakeLists.txt