Updates .unit-5-7 to the new grid system

Makes a fix to .site-name as a result, too.
Fixes .site-name bug caused by new grid fixes
Adds .grid-alt to grid system

.grid-alt allows grid orphans to be left-aligned.
Improves margins on .main-content and .sidebar

Improves margins on .main-content and .sidebar at narrow screen sizes.
Latest styles.
Merge branch 'grid-system-fixing'

Conflicts:
	sass/layout/_grid.scss