Move code examples in remarkup to grey backgrounds

Summary: This should make code easier to read. Right now large blocks get a really bright treatment, and this should tone it down. Also upped the spacing a bit.

Test Plan:
Review Remarkup Examples from Diviner, also some test code blocks and counter examples.

{F1081606}

{F1081607}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15141

resources/celerity/map.php

@@ -7,7 +7,7 @@
  */
 return array(
   'names' => array(
-    'core.pkg.css' => '8abb1666',
+    'core.pkg.css' => '5e4df064',
     'core.pkg.js' => 'a79eed25',
     'darkconsole.pkg.js' => 'e7393ebb',
     'differential.pkg.css' => '2de124c9',
@@ -103,7 +103,7 @@ return array(
     'rsrc/css/application/tokens/tokens.css' => '3d0f239e',
     'rsrc/css/application/uiexample/example.css' => '528b19de',
     'rsrc/css/core/core.css' => '5b3563c8',
-    'rsrc/css/core/remarkup.css' => '64277c02',
+    'rsrc/css/core/remarkup.css' => 'e1c8b32f',
     'rsrc/css/core/syntax.css' => '9fd11da8',
     'rsrc/css/core/z-index.css' => 'a36a45da',
     'rsrc/css/diviner/diviner-shared.css' => 'aa3656aa',
@@ -128,7 +128,7 @@ return array(
     'rsrc/css/phui/phui-crumbs-view.css' => '414406b5',
     'rsrc/css/phui/phui-document-pro.css' => '8799acf7',
     'rsrc/css/phui/phui-document-summary.css' => '9ca48bdf',
-    'rsrc/css/phui/phui-document.css' => 'a4a1c3b9',
+    'rsrc/css/phui/phui-document.css' => '9c71d2bf',
     'rsrc/css/phui/phui-feed-story.css' => 'b7b26d23',
     'rsrc/css/phui/phui-fontkit.css' => '9cda225e',
     'rsrc/css/phui/phui-form-view.css' => '4a1a0f5e',
@@ -759,7 +759,7 @@ return array(
     'phabricator-object-selector-css' => '85ee8ce6',
     'phabricator-phtize' => 'd254d646',
     'phabricator-prefab' => 'e67df814',
-    'phabricator-remarkup-css' => '64277c02',
+    'phabricator-remarkup-css' => 'e1c8b32f',
     'phabricator-search-results-css' => '7dea472c',
     'phabricator-shaped-request' => '7cbe244b',
     'phabricator-side-menu-view-css' => '3a3d9f41',
@@ -801,7 +801,7 @@ return array(
     'phui-calendar-month-css' => '476be7e0',
     'phui-crumbs-view-css' => '414406b5',
     'phui-document-summary-view-css' => '9ca48bdf',
-    'phui-document-view-css' => 'a4a1c3b9',
+    'phui-document-view-css' => '9c71d2bf',
     'phui-document-view-pro-css' => '8799acf7',
     'phui-feed-story-css' => 'b7b26d23',
     'phui-font-icon-base-css' => 'ecbbb4c2',