Add SnappyEncoder/Decoder

The encoder/decoder should work. Haven't actually hooked it into the log
namer yet, though.

Change-Id: Id20be8161d46fe080f89eee8032103977574e7ad
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/third_party/snappy/BUILD b/third_party/snappy/BUILD
index e519ee4..da308a7 100644
--- a/third_party/snappy/BUILD
+++ b/third_party/snappy/BUILD
@@ -19,4 +19,5 @@
         "snappy-stubs-public.h",
     ],
     copts = ["-Wno-sign-compare"],
+    visibility = ["//visibility:public"],
 )