Update README.md

updated instructions to be more clear for replica sets. the recipe used should be used instead of the default not in addition to
Merge pull request #241 from aciddj/patch-1

Update README.md
not sure why Regexp is expected to have anything for last_match, but added to the conditional to check for nil and that last_match[1] exists
    before attempting to use it
Merge pull request #242 from newcontext/issue_234

pull request for issue 234