Add docs explaining difference with diff-match-patch

[jvican]

Describe the bug
I'd like to know what are the differences between java-diff-utils and diff-match-patch, especially when it comes to performance. Is there a concrete reason why this library was created instead of reusing the former?

Expected behavior
There some docs in the wiki explaining the rationale behind creating this library and how it compares with diff-match-patch.

[wumpz]

To be honest, I was not aware of this project. This was derived from the known java-diff-utils from Google.