delim_whitespace deprication

[davewhipp]

delim_whitespace will be depricated in pandas, which causes warnings to be raised when reading data using pd.read_csv(). Instead, it is suggested to use sep='s+' instead. This has been updated in Chapter 4, but Chapter 3 should be checked.

[davewhipp]

Note, the correct syntax to avoid issues is sep=r"\s+".