I was trying out different rich text editors for web, they all good but I found CKEditor 4 is the easiest to set up.
Go to CKEditor Builder. Click download after you pick the plugins, skins and langauges you want. Save the CKEditor files in the server. You can delete the example folder.
<textarea id="editor"></textarea>
<!-- CK Editor Module -->
<script src="/static/ckeditor/ckeditor.js"></script>
<script src="/static/ckeditor/config.js"></script>
CKEDITOR.replace( '#editor' );
config.extraPlugins = 'imgur';
config.imgurClientId = 'Your-Client-id';