providers/os: Change name of fileExists to exists

providers/os/os.go

@@ -28,7 +28,7 @@ type Provider struct {
 func (this *Provider) FuncMap () template.FuncMap {
 	return template.FuncMap {
 		"env":        funcEnv,
-		"fileExists": funcFileExists,
+		"exists":     funcExists,
 		"isFile":     funcIsFile,
 		"isDir":      funcIsDir,
 		"statFile":   funcStatFile,
@@ -44,7 +44,7 @@ func funcEnv (name string) string {
 	return os.Getenv(name)
 }
 
-func funcFileExists (name string) (bool) {
+func funcExists (name string) (bool) {
 	_, err := os.Stat(name)
 	return err == nil
 }