split up layout and global file and clean up markup

views/layout.pug

@@ -8,7 +8,7 @@ html
       #main__header
         header.header
           .header__upper-wrapper
-            .header__upper.wrapper
+            .header__upper.layout-centered
               .header__title
                 img(src='/images/icon-info.svg')
                 span Example Application
@@ -26,7 +26,7 @@ html
                       option(value='en-US' selected=query.locale === 'en-US') English
                       option(value='de-DE' selected=query.locale === 'de-DE') German
           .header__lower-wrapper
-            .header__lower.wrapper
+            .header__lower.layout-centered
               .header__logo
                 a.header__logo-link(href='/')
                   img(src='/images/logo.svg' alt='Contentful Example App')
@@ -46,7 +46,7 @@ html
         block content
 
       #main__footer
-        .wrapper
+        .layout-centered
           footer.footer
             .footer__upper
               nav.footer__navigation.main-navigation