Changed header size in CONTRIBUTING.md

CONTRIBUTING.md

@@ -32,7 +32,7 @@ Symbologies and The Core
 ----
 JsBarcode is divided up in two distinct parts. The barcode symbologies (EAN-13, CODE128, ITF, ...) and the core.
 
-#### Symbologies
+### Symbologies
 Implementing a new symbology is the easiest way to contribute. Just follow the standard for that symbology and create a class that generate the correct binary data.
 
 The structure of such a class is as follows:
@@ -60,7 +60,7 @@ class GenericBarcode{
 
 It might be a good idea to check one of the already implemented barcodes (such as [ITF14](https://github.com/lindell/JsBarcode/blob/master/src/barcodes/ITF14/index.js)) for inspiration. 
 
-#### The Core / Renderers
+### The Core / Renderers
 The core part handles the API requests and calls the renderers. If you want to do any structural changes please [create an issue](https://github.com/lindell/JsBarcode/issues/new) or ask about it in the [gitter chat](https://gitter.im/lindell/JsBarcode) first.
 
 Bug fixes is of course welcome at any time :+1: