update readme

README.md

@@ -1,2 +1,21 @@
 # tta
-go impl for libtta/libtta++
+[TTA Lossless Audio Codec](http://en.true-audio.com/TTA_Lossless_Audio_Codec_-_Realtime_Audio_Compressor) Encoder/Decoder for #golang
+
+## [API doc](https://godoc.org/github.com/zyxar/tta)
+
+## *gotta* console tool
+
+- install: `go get github.com/zyxar/tta/cmd/gotta`
+- usage:
+
+  ```
+    -decode=false: decode file
+    -encode=false: encode file
+    -help=false: print this help
+    -passwd="": specify password
+  ```
+
+## TODOs
+
+- [ ] general optimization
+- [ ] SSE4 acceleration