Update README

Author: mattwynne

README.md

@@ -34,6 +34,9 @@ $ changelog init --compare-url=https://github.com/myorg/myrepo/compare/abcdef...
 $ changelog added "Initial commit"
 # Create release
 $ changelog release 0.1.0
+# Show latest release number
+$ changelog latest
+=> 0.1.0
 ```
 
 ## Installation
@@ -76,6 +79,7 @@ Available Commands:
   fmt         Reformat the change log file
   help        Help about any command
   init        Initializes a new changelog
+  latest      Show latest released version number
   release     Change Unreleased to [version]
   removed     Add item under 'Removed' section
   security    Add item under 'Security' section

cmd/latest.go

@@ -12,7 +12,7 @@ import (
 func newLatestCmd(iostreams *IOStreams) *cobra.Command {
 	return &cobra.Command{
 		Use:   "latest",
-		Short: "Show latest version",
+		Short: "Show latest released version number",
 		Long:  `Show version number for the top (released) entry in the changelog`,
 		Args:  cobra.ExactArgs(0),
 		RunE: func(cmd *cobra.Command, args []string) error {