Merge pull request #106 from eparis/bash-comp-docs

Make the filename extension bit of docs easier to read.

bash_completions.md

@@ -123,15 +123,18 @@ and you'll get something like
 In this example we use --filename= and expect to get a json or yaml file as the argument. To make this easier we annotate the --filename flag with valid filename extensions.
 
 ```go
-	annotations := make([]string, 3)
-	annotations[0] = "json"
-	annotations[1] = "yaml"
-	annotations[2] = "yml"
-
+	annotations := []string{"json", "yaml", "yml"}
 	annotation := make(map[string][]string)
 	annotation[cobra.BashCompFilenameExt] = annotations
 
-	flag := &pflag.Flag{"filename", "f", usage, value, value.String(), false, annotation}
+	flag := &pflag.Flag{
+		Name:        "filename",
+		Shorthand:   "f",
+		Usage:       usage,
+		Value:       value,
+		DefValue:    value.String(),
+		Annotations: annotation,
+	}
 	cmd.Flags().AddFlag(flag)
 ```