add makefile for cross compiling

.gitignore

@@ -1,3 +1,4 @@
 vendor
 *.db
 tmail
+build

makefile

@@ -0,0 +1,13 @@
+linux:
+	go build -o ./build/tmail-linux ./main.go
+
+mac:
+	GOOS=darwin GOARCH=amd64 go build -o ./build/tmail-mac ./main.go
+	
+windows:
+	GOOS=windows GOARCH=386 go build -o ./build/tmail-windows.exe ./main.go
+
+clean:
+	rm -rf ./build
+
+all: linux mac windows

readme.md

@@ -7,6 +7,8 @@ A throwaway smtp mail server with an API to retrieve emails.
 - all emails sent to *@<your domain> are stored in `mail.db`
 - hit these end points to check the email
 
+[Download the latest release here.](https://github.com/mgerb/tmail/releases)
+
 ```
 All mail:
 http://host:8090/api/mail