Add viewport meta tag to wardrobe page

Oops, this was causing the page to render in a weird zoomed-out way on mobile!

Note that, for most of the site, we intentionally haven't added this tag yet because most of our pages aren't especially responsively-designed; so we _want_ the device's best attempt to work with that, rather than trying to enforce something.

app/views/outfits/edit.html.haml

@@ -2,6 +2,7 @@
 %html
   %head
     %meta{charset: 'utf-8'}
+    %meta{name: 'viewport', content: 'width=device-width, initial-scale=1'}
     %title Dress to Impress
     %link{href: image_path('favicon.png'), rel: 'icon'}
     = stylesheet_link_tag 'fonts'