Fixed multiple h1 tags in pages

While HTML5 allows for multiple h1 tags within structural tags, most screen readers, browsers and other tools (eg search engines) treat them all as top-level elements.

I've proposed to edit Jekyll Now to only use H1 headings on the **site name on the home page**, and the on the **page titles for other pages**. I've also edited the ```style.scss``` file to ensure the theme styling remains as was on updated tags.

When using Jekyll Now as a blogging platform, I believe this'll help with SEO as well as improve HTML5 validity.