Create about page

[techieshark]

• Add About screen view as is
• Finalize content
• Style About screen
• add About screen Location and Action type
• add About screen to router
• handle location/action changes in updateModel and updateAction

[techieshark]

removed:

• add About screen to nav menu so we can get to it

Adding About screen to nav menu might make sense later when we can update it for other screens as well (and relates to #85 and #98) so I'll put it off for now. You can still view about page by manually updating the url (change #!/discover to #!/about).