Switch to com.fasterxml.jackson v2.4.4

Hi,

As promised, I have created a pull request to upgrade Jackson to a more recent version with a different group/package name.

All unit tests seem to run OK. I am not sure if the new one is faster or not.

Sincerely,
Teofilis Martisius
javadoc is not updated - `{@link Utf8StreamParser}` -> `{@link UTF8StreamJsonParser}`