Can I view changes to a GitHub hosted page before committing to master?

I host a personal website using GitHub pages and I manage the process of changing and improving the site using Git.

My process is to make changes in a 'development' branch and push these to master.

I believe this is a standard process, but my question is: Is there a way of seeing how the website changes before going through all the steps to merge with master? Or can I see and test this change earlier on, say in a test environment?

I have been trying to find an answer to this question for some time. The closest I have got to an answer is here: Can I run HTML files directly from GitHub, instead of just viewing their source?

However when using http://rawgit.com an index.md file only shows as markdown and when using http://htmlpreview.github.io/ all the markdown text appears bunched together. In both cases I can't see any styling as the website is structured using links to external styling sheets and Jekyll front matter.

How can I solve this and view the page as it is supposed to appear?