MORITA Hajime (omo) 20e566f58f Makes font-family names customizable.
This chagne instroduces following variables
that allows authors to customize a font family for each class.
- $serif
- $sans
- $heading-font-family
- $header-title-font-family

This change also adds anotehr custom scss file named "_fonts.scss".
We can use it to override these newly introduced variables.
..
_layout.scss Removes <nav> for Pagination links, fixes
_solarized.scss Fixes solarized colors, fixes
_theme.scss Make the background and the footer gradiations customizable
_typography.scss Makes font-family names customizable.
_utilities.scss using @extend for responsive blocks, added shadow-box mixin to utlities for configurable border shadow box styling, moved .left, .right, .center classes to .basic-alignment class for @extending as needed in layouts. Fixes