Use \proglang and \pkg in Keywords list for proper typesetting, add Rcpp
keyword.

Improve the table float placement significantly in section 4 by
letting latex do its own thing with [tbp] instead of trying to place
them [h] which never works.  With the default [tbp] it gets most of
the floats placed inside section 4 so section 5 is much more readable
now without being interspersed with floats from the previous section.

Improve the histogram / mr example slightly.



git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rprotobuf@823 edb9625f-4e0d-4859-8d74-9fd3b1da38cb