Add "What's new in Java Client API 3.0" section on README

[nikos]

It would be great to have mentioned the highlights of the Java Client API 3.0 (in comparison to 2.0) summarized on the README / start page of the project.

[sammefford]

Great suggestion, Niko. I'll put that together. In the meantime, you can find the new features in 3.0 summarized here. Or a broad overview here.

[sammefford]

Oh, and I should point out there is also an overview of all that's new in MarkLogic 8.0 here. It's pretty exciting!

[kcoleman-marklogic]

There is also a summary here:

http://docs.marklogic.com/guide/relnotes/chap3#id_32290

[nikos]

Great stuff, thanks a lot for taking care @sammefford