Clarified steps for new users.

- Expanded the four steps to the discrete steps outlined in the
  document.
- Clarified the steps to use the implied verbs (not "get" but "download
  and install").
- Moved the downloading of the blog skeleton from the "run" section to
  the "download and install" section as it's part of the setup.
- Fixed a couple of spelling mistakes ("let's" is "let us", "lets" is
  "permits")
- Added a space between to the sample twig output to escape the
  variable (and added a note explaining people should take this out).
  Otherwise the variable renders and you get the page title.
- Separated the publish step into two: generate production-ready site;
  and upload to the server.
- Updated the what's next section to point to the documentation, or look
  at examples of what you can build with Sculpin.
Adding verbatim blocks so the twig variables are displayed. Removed the additional note about the space in the variable.
Merge pull request #33 from emmajane/master

Clarified steps for new users.