Readme citation typo

[linikujp]

It should be:
Rose S, Engel D, Cramer N, and Cowley, W. Automatic Keyword Extraction from Individual Documents, In: Berry MW, Kogan J, editors. Text Mining: Applications and Theory. Chichester, UK: John Wiley & Sons; 2010. doi: 10.1002/9780470689646.ch1