Package assets (#1493)

* Package static assets
* Fixed cancel button in editor
* Fix rake compilation task
* Add asset path helper
* Serve MathJax statically
* Fix mathjax in preview

lib/gollum/public/assets/criticmarkup-31ae5d3282bbb8e7b7c3c9917e9fb68e3315a6b4a75da6cec48d21b8846905c4.css

@@ -0,0 +1 @@
+.criticmarkup mark{background-color:#fffd38;text-decoration:none}.criticmarkup del{background-color:#f6a9a9;text-decoration:line-through}.criticmarkup ins{background-color:#a9f6a9;text-decoration:none}.criticmarkup ins.break{display:block;line-height:2px;padding:0 !important;margin:0 !important}.criticmarkup ins.break span{line-height:1.5em}.criticmarkup .popover{background-color:#fffd38;color:#000}.criticmarkup .critic.comment{display:none}.criticmarkup .popover:hover span.critic.comment{display:block;position:absolute;width:200px;left:30%;font-size:0.8em;color:#ccc;background-color:#333;z-index:10;padding:0.5em 1em;border-radius:0.5em}

lib/gollum/public/assets/print-c70ea78d9c87a4546733a2f2288fbf1f93fa8510890ac73cac6db8a784e27429.css

@@ -0,0 +1 @@
+ul.actions{display:none}#delete-link{display:none}div#footer{display:none}

lib/gollum/public/gollum/javascript/HOWTO_UPDATE_MATHJAX.md

@@ -28,10 +28,14 @@ offline with latex equations without bloating the gollum release tarball.
 6. Slimify mathjax
 
       cd MathJax-x.y.z && grunt && cd ..
+      
+7. Remove old mathjax (careful!)
 
-7. Replace bundled mathjax with newly generated one
+     rm -rf ${GOLLUM_ROOT}/lib/gollum/public/gollum/javascript/MathJax
 
-      cp MathJax-x.y.z ${GOLLUM_ROOT}/lib/gollum/public/gollum/javascript
+8. Replace bundled mathjax with newly generated one
 
-8. Update mathjax version in ${GOLLUM_ROOT}/lib/gollum/templates/layout.mustache
+      cp MathJax-x.y.z ${GOLLUM_ROOT}/lib/gollum/public/gollum/javascript/MathJax
+
+9. Update mathjax version in ${GOLLUM_ROOT}/lib/gollum/templates/layout.mustache