command-line options.
-WHAT'S NEW in version 2.5.0 (2014-03-??)
+Version 2.6.0 (2014-06-08)
+
+ Make options -e/-i to work with multipart subparts.
+
+ Add option -I to completely ignore a part - no headers, no body,
+ no warning.
+
+ Open all output files in binary mode. Output os.linesep instead of '\n'.
+
+ Test --save-headers|body|message masks one after another to allow
+ saving a message or a subpart to more than one file.
+
+WHAT'S NEW in version 2.5.0 (2014-03-18)
Add option --set-header=header:value to set header's value (only at the top
level).