Zen Grids 1.3 includes several minor bugfixes.

Changes since 1.2:
- Refactor example project template to use best practices.
- Deprecate experimental zen/background-grid module.
- Incorrect gutter for zen-grid-flow-item() when using fixed units.
- Correct the parameter name used in warning text of zen-grid-flow-item().
- zen-grid-item-width() returns wrong width when box-sizing is content-box.
- Don't prevent top/bottom borders on content-box grid items.