Update README.md for 6.70 release.

Also list versions in reverse order (newest first), and provide better
annotations for most of the versions.

README.md

@@ -4,24 +4,47 @@ SCC: Strip C Comments — Snapshots
 This repository contains the code for the SCC (Strip C Comments) program described in
 [Remove Comments from C/C++ Code](http://stackoverflow.com/questions/2394017/) on Stack Overflow.
 
-There are currently 6 releases:
-* 4.03 (2008-06-07)
-* 4.04 (2008-11-27)
-* 5.05 (2012-01-23)
-* 6.16 (2016-01-19) — pre-release
+There are currently 7 releases:
+* 6.70 (2017-10-17) - stable release
+* 6.60 (2016-06-12) - stable release
 * 6.50 (2016-06-12) — pre-release
-* 6.60 (2016-06-12)
+* 6.16 (2016-01-19) — pre-release
+* 5.05 (2012-01-23) - stable release
+* 4.04 (2008-11-27) - stable release
+* 4.03 (2008-06-07) - stable release
 
 These are tagged release/x.yz.  The code is all on branch master.
 
+Versions 4.03 and 4.04 are preliminary versions, possibly of historical
+interest.
+Functionally, they're almost identical, with minor code cleanups between
+the two versions.
+The meaning of the `-C` option was the opposite of the more modern
+versions; it enabled the removal of C++ style comments.
+
 Version 5.05 handles C and older C++ code.
-It does not understand raw strings, or some of the other new features in C++
-(binary constants, punctuation in numbers, etc.).
+It does not understand raw strings, or some of the other new features in
+C++ (binary constants, punctuation in numbers, etc.).
+Compared to the earlier versions, it adds the `-s str` and `-q rep`
+options to replace the bodies of strings or character literals; it adds
+the `-c` option to print the comments instead of the code; it adds the
+`-n` option to preserve newlines in comments, to make it easier to
+back-track from stripped source to the original code.
 
 Version 6.60 handles C and newer C++ code.
 It understands raw strings, binary constants and punctuation in numbers.
 It has a different, slightly more complex interface compared with version 5.05.
 
-Neither version handles trigraphs (and neither version needs to handle digraphs).
-There are separate programs for adding or removing trigraphs and digraphs (called,
-unimaginatively, `trigraphs` and `digraphs`).
+Version 6.70 provides some occasionally useful new functionality.
+The `-e` option emits empty comments `/* */` or `//` (followed by a
+newline) instead of a space.
+This can simplify some code analyses.
+The `-c` option has been upgraded to generate a newline after each line
+of comments.
+This makes the output (much) easier to read.
+The flags (`-f`) option has more systematic names for the features.
+
+No version of SCC handles trigraphs (and no version needs to handle
+digraphs).
+There are separate programs for adding or removing trigraphs and
+digraphs (called, unimaginatively, `trigraphs` and `digraphs`).