Added three new compression algorithms (snappy,
lz4, and lz4hc) and did some general clean-up to
reduce the number of changes needed to add new ones
in the future. Also added a script that should make
building with CMake easier, as it seemed t
trouble with different installations (for example,
CMake's FIND_LIBRARY seemed to check only that
the library existed in a certain location, not
that it had the required permissions).