fix standard headers and header spacing in winner README.md files

1993/plummer/README.md

@@ -27,7 +27,7 @@ where:
 NOTE: an alternate version exists. See Alternate code section below.
 
 
-## Try:
+### Try:
 
 ```sh
 ./plummer 01234567890876543210 xxx
@@ -64,6 +64,7 @@ make clobber CDEFINE="-DZ=50" alt
 For extra credit: What happens when 'number' contains non-numeric
 characters, and why?
 
+
 ## Author's remarks:
 
 This program prints out all numbers up to a given number of digits