Add a missing article in the mapreduce/histogram application section
and try using \begin{Code} instead of \begin{verbatim} in that section
(seems to be typeset the same, I may try more changes to improve the
typsetting of this example).

Steve Scott noticed that one sentence in the conclusion had the word
'other' in it 3 times -- remove one superfluous word as he suggested.

Split another run-on sentence in the conclusion into two sentences as
suggested by Steve as well.



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rprotobuf@821 edb9625f-4e0d-4859-8d74-9fd3b1da38cb