Update readme.md

Author: mateuszstompor

README.md

@@ -6,7 +6,7 @@ Repository contains Ruby implementation of space partitioning tree data structur
 It is a form of binary tree meant to provide a efficient way of objects retrieval.
 Detailed description can be found [here](https://en.wikipedia.org/wiki/K-d_tree)
 
-# Usage
+### Usage
 ```ruby
     # Import the library to your project
     require 'kd_tree_ms'
@@ -48,11 +48,11 @@ Detailed description can be found [here](https://en.wikipedia.org/wiki/K-d_tree)
     tree.size
 ```
 
-# Approach
+### Approach
 The Tree was implemented in TDD approach. 
 There are many simple, easy to read tests, written with help of MiniTest gem
 
-# Installation
+### Installation
 * Download or clone repository
 * Navigate to the root folder of the project
 * Build gem with command:
@@ -64,8 +64,8 @@ There are many simple, easy to read tests, written with help of MiniTest gem
     $ sudo gem install kd_tree_ms-1.0.0.gem
 ```
 
-# Contributing
+### Contributing
 Contributions are welcome! Please fork the repository and submit a pull request. For major changes, please open an issue first to discuss what you would like to change.
 
-# Contact
+### Contact
 For support or inquiries, please open an issue on the [GitHub repository](https://github.com/mateuszstompor/kdtree/issues).