update reference materials

Merge branch 'issue-25':

These commits fix issues related to the use of a new, default, RNG method
in R-devel (to be 3.6.x), which was causing failures in unit tests and
differences in outputs of examples/vignettes etc. This is fixed temporarily
here. A broader fix might be to require R >= 3.6.0 when it is released.
Closes #25

bump to 0.9-4 and document in NEWS

fix URLs to CRAN canonical form

document 0.9-2 in NEWS

Document changes in 0.9-1

change date to actual release date

update the Description field to match latest requirements in WRE