Create README.md

Author: ysonggit

README.md

@@ -0,0 +1,24 @@
+# leetcode-ruby
+
+Ruby-Graphviz library needs to be installed in order to use drawTree() function
+
+Source at: https://github.com/glejeune/Ruby-Graphviz
+
+```bash
+gem install graphviz
+
+gem install ruby-graphviz
+```
+
+For a binary tree, like below
+```
+    1
+  /   \
+ 2     3
+        \
+         4
+```
+
+the function will generate a png file in the same directory as below: 
+
+![img](http://i.imgur.com/b50jywY.png)