Support saving and loading history

[nemith]

Need a way to save and load history. Should use os.Reader and os.Writer as well as convenience functions to load and save from a file.

[mattyhall]

Hi, it's the person from reddit.

I added the helper functions in my fork of the project (https://github.com/mattyhall/go-goline). Hopefully everything is up to scratch, however some of it is a bit messy - particularly when, in history.Load, the writer is turned into a bufio writer.

With regards to exposing this to the user I can think of a couple of ways of doing this:

• Pass a filename at start and automatically save after each enter
• Have a SaveHistory function on GoLine which calls the same function on History which is called when the programme is done

Obviously if what I've done so far isn't too good feel free to say!

Thanks