Switch order of mapreduce/web services sections in the last paragraph
of the intro since we've moved the order of them in the text.

For a figure in the mapreduce example section, make the histogram
more vertically compact to not waste so much space.



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rprotobuf@799 edb9625f-4e0d-4859-8d74-9fd3b1da38cb