Removed mark2 support from the cookbook.

Upstream has declared mark2 as "on life-support" so it was decided
to no longer support it.

Read more here:

http://www.reddit.com/r/admincraft/comments/1s1t4e/the_state_of_mark2_and_the_path_forward/

This also bumps minecraft to 1.7.4 now that we are not waiting on
mark2 bugs to be fixed.