Update 2013-03-14-using-bigmemory-with-rcpp.md

Added the BH dependency to the Rcpp header (required to compile successfully), and added a note about package development (you need C++11 as a SystemRequirement to compile without warnings).
Yes, see commit  https://github.com/jjallaire/rcpp-gallery/commit/a2c368bb49c1d669f02bbc081ef590ebdee85e41