Updated R targets to use r-package build-type.
Removed MASS package target.

This is now packaged with R and isn't available on CRAN.
Added local-repository option description.
Merge pull request #45 from jrrideout/qiime-deploy-issue-3

Support for new r-package build-type.
Added to local-repository description.
Merge branch 'master' into qiime-deploy-issue-24
Updated r-package description.

Now references local-repository.
Merge pull request #46 from jrrideout/qiime-deploy-issue-24

Updated OPTIONS to document local-repository option.