Add rake

Add a rake to import [ITIS CSV](https://dl.dropboxusercontent.com/u/4378314/itis-plants.csv). 

This only imports Plant names in English, and their Latin names. No description, no nothing. Just names. 
What's the deal with this limit, anyway? I noticed @warpling touched it some time ago and I was really confused why the limit was set to 2. Can you explain this one @warpling ?