Typography, colour and spacing changes for preview.
- Let OC manage default font (looks nicer)
- Improve style, size and spacing of heading elements
- Remove top margin from <li> elements
- Use numbering on <ol> elements
- Remove left border, add slight background tint.
Add Highlight.js support for code syntax highlighting.
Fix top of preview falling unber oC navigation bar (only tested in oC7).
Using a fixed px value rather than em, since the oC7 title and navgation bars are as big as they are, and not variable.
Better spacing for lists.
Update preview in readme.
Revert "Update preview in readme."

This reverts commit ccac2d1987b66fe76c3eb101fff275c77dfb3a61.
Update readme screenshot
Update readme latex screenshot
Fixes issue #6
Applies right and centre alignment via CSS selectors where Marked has specifically defined cell alignment attributes.
Merge branch 'master' of https://github.com/shrimpza/owncloud-markdown
Merge pull request #7 from shrimpza/master

CSS Updates and Highlight.js