Bump the version to a string

Previously we'd bump to a float, which is incorrect, and couldn't be parsed
when we attempted to bump the version again.

Makefile

@@ -0,0 +1,10 @@
+.PHONY: test
+
+install:
+	go install ./...
+
+test:
+	go test -race ./... -timeout 1s
+
+release: install test
+	bump_version minor main.go

lib/lib.go

@@ -157,7 +157,7 @@ func BumpInFile(vtype VersionType, filename string) (*Version, error) {
 				if err != nil {
 					return nil, err
 				}
-				value.Value = version.String()
+				value.Value = fmt.Sprintf("\"%s\"", version.String())
 				f, err := os.Create(filename)
 				if err != nil {
 					return nil, err

main_test.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestVersionString(t *testing.T) {
+	typ := reflect.TypeOf(VERSION)
+	if typ.String() != "string" {
+		t.Errorf("expected VERSION to be a string, got %#v (type %#v)", VERSION, typ.String())
+	}
+}