biocore/emp: Release for manuscript publication (doi:10.1038/nature24621)

Release of the EMP GitHub repository for archiving in Zenodo (DOI: 10.5281/zenodo.1009693) for publication of the manuscript on EMP 16S Release 1 in Nature. The title of that manuscript is "A communal catalogue reveals Earth's multiscale microbial diversity", and its DOI is 10.1038/nature24621