Refactor repository layout and convert build system to Mage.

This commit implements a massive refactor of the repository, and
moves the build system over to use Mage (magefile.org) which should
allow seamless building across multiple platforms.

vendor/github.com/magefile/mage/bootstrap.go

@@ -0,0 +1,19 @@
+//+build ignore
+
+package main
+
+import (
+	"os"
+
+	"github.com/magefile/mage/mage"
+)
+
+// This is a bootstrap builder, to build mage when you don't already *have* mage.
+// Run it like
+// go run bootstrap.go
+// and it will install mage with all the right flags created for you.
+
+func main() {
+	os.Args = []string{os.Args[0], "-v", "install"}
+	os.Exit(mage.Main())
+}