change README

README.md

 pika
 ====
 
-A network program framework according to the SEDA Paper.
-Some ideas may copy from the linshiding's Kyling
+Pika is a simple nosql database.
+Pika used leveldb as storage engine.
+The protocol used to contact with Pika is defined in google's proto buffer, The
+proto buffer file is bada_sdk.proto
+
+### Thread Model
+Pika used multi threads model. The main thread accept the request and then send
+the request to the work threads.
+
+Pika written all in C++
 
 Just for fun ^-^