removed blank line

removing the blank line prevents the error: “Error : contains a blank
line”
lowercase change

Change the name of MCAR.test to mcar_test, as I think this looks nicer
and keeps the lowercase trend Hadley recommends.
minor change

ran `document()` and it removed this line.
new .Rd from `document`

Ran `document()` on the slightly changed mcar_test (previously
MCAR.test) and it reproduced the .Rd file.
change from renaming

change in the NAMESPACE from renaming the MCAR.test function to
mcar_test().
added rpart

ran the rpart function to predict the cluster from  `hclust()` when cut
point is 4.