Add article guidelines to README
Article guidelines: Fix some typos
Merge pull request #7 from fza/feature/article-guidelines

Add article guidelines to README
Implement missing Markdown styles
Merge pull request #8 from rasshofer/feature/markdown-styles

Implement missing Markdown styles
Update gulp-sass to 1.2.3, so the quick fix in #1 becomes obsolete
Add CC-BY-SA stmt in footer, refactor SCSS, replace images with SVG, tune gulpfile