reduce UV thread-pool size to 16

libraries/metrics/uv_threadpool_size.coffee

@@ -1,2 +1,2 @@
-process.env.UV_THREADPOOL_SIZE=128
-console.log "Set UV_THREADPOOL_SIZE=#{process.env.UV_THREADPOOL_SIZE}"
+process.env.UV_THREADPOOL_SIZE=16
+console.log "Set UV_THREADPOOL_SIZE=#{process.env.UV_THREADPOOL_SIZE}"