Merge pull request #6 from ropensci/master

Um.  I might be doing something wrong.
Fixing `README.md` to resolve issue #97.

* Changing the plotting for both the mammoth and publication example.
* Changes to `get_publication` to improve `data.frame` behavior by setting `stringsAsFactors=FALSE`.
*  New plots for mammoth and publications.
Merge pull request #102 from SimonGoring/master

Improvements to README and `get_publication`.