Adding subtitles to simplify TOC

Author: it33

source/developer/developer-setup.md

@@ -177,6 +177,8 @@ Any issues? Please let us know on our forums at: http://forum.mattermost.org
 
 ## Troubleshooting
 
+### Build errors 
+
 #### I get the following error when running `make run` on Mac OS X: "Cannot connect ot the Docker daemon"
 
 If you have Docker Tools installed (as opposed to Docker for Mac), you need make sure `docker-machine` is running with the following:
@@ -198,6 +200,8 @@ There's likely another Mattermost instance already running. You can use `make st
 
 If there isn't another copy of Mattermost running and you need to change the port that Mattermost is running on, you can do so by changing the `ListenAddress` setting in the `ServiceSettings` section of `config/config.json`.
 
+### Other errors 
+
 #### I don't see any error messages, but I can't access `http://localhost:8065`
 
 It's possible that the server reported an error, but it was missed because of all of the output from the Javascript compiler. Try running `make run-server` by itself to see its output. If you still don't see any error messages, continue to the next section.