Adding Support for Empty Values

**Why:**

* This allows the responses to customized if params aren't set

**This change addresses the need by:**

* closes #5

Signed-off-by: Christopher Hein <me@christopherhein.com>

version.go

@@ -2,14 +2,14 @@ package version
 
 import (
 	"encoding/json"
-	"fmt"
+	"strings"
 )
 
 // Info creates a formattable struct for output
 type Info struct {
-	Version string
-	Commit  string
-	Date    string
+	Version string `json:"Version,omitempty"`
+	Commit  string `json:"Commit,omitempty"`
+	Date    string `json:"Date,omitempty"`
 }
 
 // New will create a pointer to a new version object
@@ -28,7 +28,29 @@ func (v *Info) ToJSON() string {
 }
 
 // ToShortened converts the Info into a JSON String
-func (v *Info) ToShortened() string {
-	str := fmt.Sprintf("Version: %v\nCommit: %v\nDate: %v\n", v.Version, v.Commit, v.Date)
-	return str
+func (v *Info) ToShortened() (str string) {
+	var version, commit, date string
+	if v.Version != "" {
+		version = "Version: " + v.Version
+	}
+	if v.Commit != "" {
+		commit = "Commit: " + v.Commit
+	}
+	if v.Date != "" {
+		date = "Date: " + v.Date
+	}
+	values := []string{version, commit, date}
+	values = deleteEmpty(values)
+	str = strings.Join(values, "\n")
+	return str + "\n"
+}
+
+func deleteEmpty(s []string) []string {
+	var r []string
+	for _, str := range s {
+		if str != "" {
+			r = append(r, str)
+		}
+	}
+	return r
 }