* Getting rid of old cheat sheets

*   Indenting error output cells
*   Removing explicit 'level' keys from Markdown files
*   Storing the generated files so that people who don't use those tools won't have to regenerate them.
*   Modifying .gitignore to reflect this.
*   Updating the Makefile to run Jekyll exactly once.
*   Command to install on the server
*   No longer worrying about making a page of images
*   Better (more guessable) name for the target that builds the website
*   Fixing image paths
*   Fixing up glossary entries

lesson.css

@@ -51,6 +51,7 @@ div.out:before {
 /* Error output. */
 .err {
     color: darkred;
+    margin-left: 20px;
     font-style: italic;
     font-weight: bold;
 }