Update README, try to cross-compile only on tags

.travis.yml

@@ -14,8 +14,11 @@ deploy:
     repo: zellyn/diskii
     tags: true
 after_success:
-  - go get github.com/inconshreveable/mousetrap
-  - mkdir -p release
-  - GOOS=linux GOARCH=amd64 go build -o release/diskii-linux-amd64
-  - GOOS=darwin GOARCH=amd64 go build -o release/diskii-macos-amd64
-  - GOOS=windows GOARCH=amd64 go build -o release/diskii-windows-amd64.exe
+  # Cross-compile tagged releases.
+  if ([ "$TRAVIS_BRANCH" == "master" ] || [ ! -z "$TRAVIS_TAG" ]) && [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
+    go get github.com/inconshreveable/mousetrap
+    mkdir -p release
+    GOOS=linux GOARCH=amd64 go build -o release/diskii-linux-amd64
+    GOOS=darwin GOARCH=amd64 go build -o release/diskii-macos-amd64
+    GOOS=windows GOARCH=amd64 go build -o release/diskii-windows-amd64.exe
+  fi

README.md

@@ -27,7 +27,9 @@ Discussion/support is in
 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).
+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).
 
 Current disk operations supported:
 
@@ -46,8 +48,8 @@ request or open an issue.
 
 ### Short-term TODOs/roadmap
 
-- [x] Build per-platform binaries for Linux, MacOS, Windows
-- [ ] Implement CATALOG, deletion, and creation of files in DOS 3.3 images
+- [x] Build per-platform binaries for Linux, MacOS, Windows.
+- [ ] Implement CATALOG, deletion, and creation of files in DOS 3.3 images.
 
 ### Related tools