Add 2004/sds/try.sh + format/typo checks

The try.sh script runs what used to be in the try section.

Format/typo fix README.md in full. This commit also fixes an
inconsistency where the author unwittingly used the word stenography
instead of steganography, a very easy mistake to make and one that I
almost missed.

Updated Makefile to silence a couple warnings.

Updated .gitignore.

2004/sds/.gitignore

@@ -8,3 +8,4 @@ sds_msg
 sds_msg.c
 sds.orig
 prog.orig
+remarks.md