Format 2013/dlowe, new script, rename others etc.

The demo.sh was renamed try.sh to be like the other entries.

The new script diff.sh runs some commands that I had previously added
(to demonstrate the entry) but which would be better in a script.

Renamed sflen.sh (for sparkline file length) to be slflen.sh (for
sparkline file length also).

Updated bugs.md - added more features that the author noted.

Format/typo check README.md file.

This should complete the review of 2013/dlowe.

bugs.md

@@ -2876,6 +2876,12 @@ exercise to see if you understand the code.
 You can try and answer the questions, too: when will it crash? When will it draw
 something funny (or will it? :-) ) and when will it just do nothing?
 
+The author also stated:
+
+* Produces bogus graphs when given > about 5000 arguments.
+* Only works if your terminal is UTF-8 and your font supports the 8 glyphs
+  used.
+
 
 ## 2013 hou