Typo

Closes #128

functions.Rmd

@@ -127,7 +127,7 @@ rescale01 <- function(x) {
 rescale01(x)
 ```
 
-This is an important part of the "do not repeat yourself" (or DRY) principle. The more repetition you have in your code, the more places you need to remember to update when things change (and they always could!), and the more likely you are to create bugs over time.
+This is an important part of the "do not repeat yourself" (or DRY) principle. The more repetition you have in your code, the more places you need to remember to update when things change (and they always do!), and the more likely you are to create bugs over time.
 
 ### Practice