Compile SASS on Gulp serve task

Solution to issue #307 - compile SASS on running "grunt serve"
I'm not sure I added that one in. https://github.com/webmakersteve/web-starter-kit/blob/e06212cce9cc7d1c2564bf87d43072b931683ee9/gulpfile.js#L185 The whitespace is still there the commit before mine.