Styling has Disappeared Since 1.5

Hey - upgraded this plugin to the latest version v1.5.0 however it seems to have lost its ability to style `

` text. 


I have the site in a dev location and production one running the older version of the plugin and when you inspect the page you find that it is reading CSS stile from .hljs (in my case style sheet vs2015). 

In 1.5 there this style sheet simply is not included. 

I have tried:

- Clear Cache

- Disabled CSS & JS Pipeline

- Custom Base URL changed to empty

I simply can't get the style sheet included. Any help would be much appreciated. Thanks

Compare the plugin's v1.5.0 asset and configuration handling with the older working version, focusing on why the Highlight.js stylesheet is no longer included. Reproduce the issue in a development site and verify that the .hljs stylesheet is loaded and styles

 text after the fix.

Written by the indexing model from the issue text.