add Cassandra

weed/filer2/cassandra/README.txt

@@ -0,0 +1,12 @@
+1. create a keyspace
+
+CREATE KEYSPACE seaweedfs WITH replication = {'class':'SimpleStrategy', 'replication_factor' : 1};
+
+2. create filemeta table
+
+ CREATE TABLE filemeta (
+    directory varchar,
+    name varchar,
+    meta blob,
+    PRIMARY KEY (directory, name)
+ ) WITH CLUSTERING ORDER BY (name ASC);