bug fix: prettyForestplot bugs

[Kdreval]

I have recently broken the prettyForestplot. This PR fixes the bugs described in #166

[mattssca]

Thanks, Kostia! I will approve this PR with a minor comment that you can deal with as you like. Since dplyr is specified under import, and because the mutate function does not have any conflicting function names from any other package, it is not necessary to specify the package before calling this function (i.e mutate::dplyr). It can simply just be mutate. Thanks!

[Kdreval]

Thanks, Kostia! I will approve this PR with a minor comment that you can deal with as you like. Since dplyr is specified under import, and because the mutate function does not have any conflicting function names from any other package, it is not necessary to specify the package before calling this function (i.e mutate::dplyr). It can simply just be mutate. Thanks!

Oh good! Thanks for the update!