Fix broken markdown list rendering

CONTRIBUTING.md

@@ -189,10 +189,10 @@ computer.  To do this you will need:
   - [SASS](http://sass-lang.com/) Compiler
   - [highlights](https://github.com/perl6/atom-language-perl6) (optional; requires
     `nodejs`, `npm`, and at least GCC-4.8 on Linux to be installed. Running `make` will set everything up for you.)
-        - Debian instructions:
-            - Get more modern nodejs than in repos: `curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -`
-            - Run `make init-highlights` to initialize highlights
-            - If that still isn't working try running `npm install node-gyp -g` and try running make command again
+    - Debian instructions:
+      - Get more modern nodejs than in repos: `curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -`
+      - Run `make init-highlights` to initialize highlights
+      - If that still isn't working try running `npm install node-gyp -g` and try running make command again
 
 ### Dependency installation