updated readme

README.md

@@ -1,10 +1,31 @@
 # A sample tree and parent-child relationship in Rust
 
+## Tree structure
+
+```rust
+
+pub struct Tree {
+    pub root: Option<TreeNodeRef>,
+}
+
+pub struct TreeNode {
+    pub uuid: Uuid,
+    pub number: u32,
+    pub text: String,
+    pub parent: Option<TreeNodeRef>,
+    pub children: Option<Vec<TreeNodeRef>>,
+}
+
+pub type TreeNodeRef = Rc<RefCell<TreeNode>>;
+```
+
 ## Sample methods
 
-- new()
-- add_child()
-- count()
-- search()
-- remove()
-- flatten()
+- new
+- add_child
+- count
+- search
+- remove
+- flatten
+
+### Please look at tests in [src/tree.rs](src/tree.rs) for more details