Function escape 

pub fn escape(unescaped_str: &str) -> RUMString

Turn UTF-8 character into escaped character sequence as expected in HL7

Example

 use rumtk_core::strings::{escape};
 let message = "I ❤ my wife!";
 let escaped_message = escape(&message);
 assert_eq!("I \\u2764 my wife!", &escaped_message, "Did not get expected escaped string! Got {}!", &escaped_message);