Make fitfuns more quiet

[gokceneraslan]

Added quietly=TRUE option to requireNamespace calls in fitfuns.R, otherwise it looks like this:

[hofnerb]

Great! Thanks a lot.

I didn't run into this issue as I usually load the required packages in advance but you are obviously right. (however, the multitude of messages only occurs with parallelized code execution; executed sequentially, it will only show the load message once).

[coveralls]

Coverage remained the same at 80.595% when pulling af88570 on gokceneraslan:patch-1 into c28d5af on hofnerb:master.