On bug fix and small suggestions

[remlapmot]

Hi there

I have had a quick look.

I have fixed a bug - on lines 318-9 of R/functions.R

standard_normal_random_effect<-mr.divw:::standard_normal_random_effect
gamma_coef<-standard_normal_random_effect*(h/sqrt(s))*sqrt(2)

should likely be (because the standard_normal_random_effect object doesn't exist in the package)

gamma_coef<-stats::rnorm(p)*(h/sqrt(s))*sqrt(2)

Also I have made several other CRAN style fixes as per my commit messages.

All the best
Tom