On POSIX filenames are case-sensitive

[raffaem]

I am trying to compile the book into a PDF and i'm getting the following error:

'``
Quitting from lines 258-259 (book.Rmd)
Error in knitr::include_graphics(file.path(img_path, "RStudio.png")) :
Cannot find the file(s): "R/img/RStudio.png"

That file, in fact, is called "rstudio.png" and not "RStudio.png"

[rafalab]

This is fixed. Thanks.