Add tests checking that Markdown submitted for a bounty's description is converted to HTML when displayed.
Update gems to latest versions.
Implement Markdown rendering for the bounty.desc property.
Merge branch 'feature-markdown-editor'

Conflicts:
	spec/features/bounty/show_page_spec.rb
Update gems to latest versions.
Add tests ensuring that unusual Unicode characters and dangerous content are handled correctly if they are input from the bounty#edit page.