update readme

README.md

@@ -1,2 +1,46 @@
 # leveldb.nim
-LevelDB wrapper for Nim
+A LevelDB wrapper for Nim in a Nim friendly way.
+
+Create a database:
+```Nim
+   import leveldb
+   import options
+
+   var db = leveldb.open("/tmp/mydata")
+```
+
+Read or modify the database content:
+```Nim
+   assert db.getOrDefault("nothing", "") == ""
+
+   db.put("hello", "world")
+   db.put("bin", "GIF89a\1\0")
+   echo db.get("hello")
+   assert db.get("hello").isSome()
+
+   var key, val = ""
+   for key, val in db.iter():
+     echo key, ": ", repr(val)
+
+   db.delete("hello")
+   assert db.get("hello").isNone()
+```
+
+Batch writes:
+```Nim
+   let batch = newBatch()
+   for i in 1..10:
+     batch.put("key" & $i, $i)
+   batch.delete("bin")
+   db.write(batch)
+```
+
+Iterate over subset of database content:
+```Nim
+   for key, val in db.iterPrefix(prefix = "key1"):
+     echo key, ": ", val
+   for key, val in db.iter(seek = "key3", reverse = true):
+     echo key, ": ", val
+
+   db.close()
+```