Fixed prediction command for splines on the test set

This change addresses a little typo in the function to predict on the test set.  Because "age" isn't a valid argument for predict.bs, the command "predict(bsBasis,age=testing$age)" just re-outputs the splines that were already generated on the training set.

The corresponding HTML and .md files will need to be regenerated after this change.  I considered including them in another commit, but it made the diffs crazy and I thought it would just confuse the issue.