add method to get diff statistics

[vendeeglobe]

I'd like to have a option to add diff statistics for the diff meta header.

example:
Added - 5 lines, deleted - 10 lines, updated - 2 lines, unmodified - 250 lines

see: jfcherng/php-diff@4b170cd

[JBlond]

@vendeeglobe There is now #100
However I haven't tested it enough. The number of not modified lines seems to be odd so far.

[vendeeglobe]

It seems it counts the chunks and not the lines.

[JBlond]

I killed the old branch and started over.
https://github.com/JBlond/php-diff/tree/php-diff-97
At least it looks good for the side by side.

Still WIP.

[JBlond]

this has bens solved with #108