update README to point to Makefile

README.md

@@ -16,6 +16,16 @@ https://stacktoheap.com/blog/2013/01/06/using-mailmap-to-fix-authors-list-in-git
 
 ## Install
 
+Find your target operating system (darwin, windows, linux) and desired bin
+directory, and modify the command below as appropriate:
+
+    curl --silent --location --output=/usr/local/bin/write_mailmap https://github.com/kevinburke/write_mailmap/releases/download/0.2/write_mailmap-linux-amd64 && chmod 755 /usr/local/bin/write_mailmap
+
+On Travis, you may want to create `$HOME/bin` and write to that, since
+/usr/local/bin isn't writable with their container-based infrastructure.
+
+The latest version is 0.2.
+
 If you have a Go development environment, you can get the binary by running the
 following:
 
@@ -29,15 +39,19 @@ go get -u github.com/kevinburke/write_mailmap
 write_mailmap > AUTHORS.txt
 ```
 
-You can put it in a Makefile like this:
+You can put it in a Makefile like this. Run `make authors` and the dependencies
+will automatically download.
 
 ```
 WRITE_MAILMAP := $(GOPATH)/bin/write_mailmap
 
 $(WRITE_MAILMAP):
-	go get -u github.com/kevinburke/write_mailmap
+	curl --silent --location --output=$(WRITE_MAILMAP) https://github.com/kevinburke/write_mailmap/releases/download/0.2/write_mailmap-linux-amd64
+	chmod 755 /usr/local/bin/differ
+
+force: ;
 
-AUTHORS.txt: $(WRITE_MAILMAP)
+AUTHORS.txt: force | $(WRITE_MAILMAP)
 	write_mailmap > AUTHORS.txt
 
 authors: AUTHORS.txt