moved CONTRIBUTING section from README into CONTRIBUTING.md
Stylesheet scaffold updates
- Added _config.scss for configuring themes/plugins
- Changed user style scaffold to _style.scss
- Updated sass-globbing gem (supporting optional imports)
- Themes now default to _index.scss, plugins to _style.scss
Merge pull request #1263 from codebykat/2.1

moved CONTRIBUTING section from README into CONTRIBUTING.md
Update CONTRIBUTING.md with a bit more info.
Make CONTRIBUTING file extname consistent with the other markdown files.
Fixed config-tag bug where it would not work for dot notation in keys. The plugin is now broken out into a plugin and a helper.