update to HTML of new_page.slim. remove bootstrap code in favor of bass-tacks
small updates to error page html
update not found page to reflect style of rest of the website
dashboard clean up. remove needless twitter divs
update visual of top right screenshot/web address area
small clean ups to text editor.
The default HTML in a new site’s `index.html` and `not_found.html` has 2-space indents. Setting the editor to match that makes the page easier to edit, because the user can use the Tab key for indentation.
This change is untested. The API call was copied from https://github.com/ajaxorg/ace/wiki/Embedding-API.