add README

README.md

@@ -1,13 +1,26 @@
 # timing
 
-A Clojure library designed to ... well, that part is up to you.
+Timing is a simple library to log call time using perf4j.
 
 ## Usage
 
-FIXME
+Just wrap forms you want to calculate call time:
+
+```clojure
+(timed :tag
+  (look-up-db ...)
+  (assemble-data ...))
+```
+
+Note that you have to provide a `tag` to identify these forms in
+timing log.
+
+Timing will select a logging provider automatically by looking up your
+classpath (slf4j, log4j and stderr). Timing doesn't depend on any
+logging provider at compile time.
 
 ## License
 
-Copyright © 2012 FIXME
+Copyright © 2012 [Sun Ning](http://github.com/sunng87)
 
 Distributed under the Eclipse Public License, the same as Clojure.