Check that retriever is on the path at package load. If it is not print a warning message.
Change print() functions to cat() functions which do the same thing but don't add "[1]" to the printed line
Change message printing from cat(string) to writeLines(strwrap(string)) per #30
Improve warning message by providing the retriever download url and by providing Mac users a modified set of instructions indicating they will have to manually add retrieve to the path.  Windows and Linux users will recieve the same message that they should just upgrade to the newest version of the retriever which will be automattically added to their path.
Merge pull request #30 from dmcglinn/retriever_check

Check that the retriever is on the path at package load