Add file mode to body processors

[jptosso]

There are two ways it can be done, we could change

Read(reader io.Reader, mime string, storagePath string) error
// To
Read(reader io.Reader, mime string, storagePath string, fileMode fs.FileMode) error

Or we could create a new way to send parameters to the Read function, like

Read(options types.BodyBufferOptions) error

It must be solved before relasing v2

[jptosso]

Implemented in #123, new type bodyprocessors.Options

// Options are used to inform a body processor where and how
// to store the data
type Options struct {
	// Mime is the type of the body, it may contain parameters
	// like charset, boundary, etc.
	Mime string
	// StoragePath is the path where the body will be stored
	StoragePath string
	// FileMode is the mode of the file that will be created
	FileMode fs.FileMode
}