Add FileManager.Open (#182)

* Add FileManager.Open

* Add Open to the FileManager interface

Author: godrei

fileutil/fileutil.go

@@ -7,6 +7,7 @@ import (
 
 // FileManager ...
 type FileManager interface {
+	Open(path string) (*os.File, error)
 	Remove(path string) error
 	RemoveAll(path string) error
 	Write(path string, value string, perm os.FileMode) error
@@ -21,6 +22,11 @@ func NewFileManager() FileManager {
 	return fileManager{}
 }
 
+// Open ...
+func (fileManager) Open(path string) (*os.File, error) {
+	return os.Open(path)
+}
+
 // Remove ...
 func (fileManager) Remove(path string) error {
 	return os.Remove(path)