Add option to #markdown_with_heading to create nav for styleguide
section.

Signed-off-by: Nicole Sullivan <nsullivan@pivotal.io>
Add option to hologram_config to include section nav.

Signed-off-by: Nicole Sullivan <nsullivan@pivotal.io>
Add include_section_nav to default config file

Signed-off-by: Geoff Pleiss <gpleiss@pivotal.io>
Make subnav configurable to top level or all sections

Signed-off-by: Geoff Pleiss <gpleiss@pivotal.io>
Add class styleguide to hologram elements

Signed-off-by: Geoff Pleiss <gpleiss@pivotal.io>
Merge branch 'feature/section_nav'
Merge branch 'feature/add_class_on_hologram_elements'

Conflicts:
	lib/hologram/document_block.rb