README: Fix example, add note about message limit

Author: woodruffw

README.md

@@ -59,7 +59,7 @@ To extract a message from a binary:
 ```bash
 $ steg86 extract bash.steg > my_message
 $ cat message
-here is my secret message!
+here is my secret message
 ```
 
 `steg86 extract` will exit with a non-zero status if a message cannot be extracted (e.g.,
@@ -114,6 +114,9 @@ implemented in *steg86*.
 
 ### Future improvements
 
+* *steg86* currently limits the embedded message to 16KB. This is a purely artificial limitation
+that could be resolved with some small format changes.
+
 * x86 (and x86_64) both have multi-byte NOPs, for alignment purposes. Additional information can be
 hidden in these in a few ways:
   * The `OF 1F /0`  multi-byte NOP can be up to 9 bytes, of which up to 5 are free