Merge branch 'feature/rouge-2.0.4' into 'master'

upgrade rouge to 2.0.5

## What does this MR do?
Upgrades Rouge to 2.0.5

## Are there points in the code the reviewer needs to double check?
No

## Why was this MR needed?
New lexers and bugfixes from upstream.

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5351

Gemfile.lock

@@ -578,7 +578,7 @@ GEM
       railties (>= 4.2.0, < 5.1)
     rinku (2.0.0)
     rotp (2.1.2)
-    rouge (2.0.3)
+    rouge (2.0.5)
     rqrcode (0.7.0)
       chunky_png
     rqrcode-rails3 (0.1.7)