Changing heading level of 'Alternate code'

Change level 3 (###) to level 2 (##):

    sgit -e 's/^### \(Alternate code\)/## \1/g' '*README.md'

which is the same as:

    sgit -e 's/^### Alternate code/## Alternate code/g' '*README.md'

This is per discussion in GitHub.

2012/zeitak/README.md

@@ -28,7 +28,7 @@ try [incorrect.c](incorrect.c) and the program itself.
 NOTE: it prints an error and exits on the first nesting error so it will not
 detect multiple issues!
 
-### Alternate code:
+## Alternate code:
 
 An alternate version of this entry, [zeitak.alt.c](zeitak.alt.c), is provided.
 The file [zeitak.alt.c](zeitak.alt.c) provides a version that has been slightly