Markdown upgrades

Fix the link example in the markdown help
Create a new method/URL that recieves markdown code in POST and displays
in (for asynch. previews)
Bootstrap and Create Tournament form style changes

Bootstrap icons are in /images/ and not /img/ as was indicated

Create Tournament form now has markdown preview and help buttons, the
admins and teams are floated and the labels and legends have slightly
modified styles
Notes markdown preview

Notes markdown can be previewed in create a tournament page. Markdown
help is also loaded inline.