Update README to mention library goals

README.md

@@ -3,21 +3,28 @@ diskii
 
 diskii is a commandline tool for working with Apple II disk images.
 
+It is also a library of code that can be used by other Go programs.
+
 Its major advantage is that it's written in Go, hence cross-platform.
 
 Its major disadvantage is that it mostly doesn't exist yet.
 
 [![Build Status](https://travis-ci.org/zellyn/diskii.svg?branch=master)](https://travis-ci.org/zellyn/diskii)
 
-Eventually, it aims to be a comprehensive disk image manipulation
-tool, but for now only the `applesoft decode` command works.
-
-It is pronounced so as to rhyme with "whiskey".
+It rhymes with “whiskey”.
 
 Discussion/support is in
 [#apple2 on the retrocomputing Slack](https://retrocomputing.slack.com/messages/apple2/)
 (invites [here](https://retrocomputing.herokuapp.com)).
 
+### Goals
+
+Eventually, it aims to be a comprehensive disk image manipulation
+tool, but for now only the `applesoft decode` command works.
+
+The library code aims (a) to support the commandline tool operations, and (b) to replace the "read and write disk images" code of the [goapple2 emulator](https://github.com/zellyn/goapple2).
+
+
 ### Installing/updating
 Assuming you have Go installed, run `go get -u github.com/zellyn/diskii`
 
@@ -26,7 +33,7 @@ Assuming you have Go installed, run `go get -u github.com/zellyn/diskii`
 - [ ] Build per-platform binaries for Linux, MacOS, Windows
 - [ ] Implement CATALOG, deletion, and creation of files in DOS 3.3 images
 
-### Similar tools
+### Related tools
 
 - http://a2ciderpress.com/
 - http://applecommander.sourceforge.net/