Merge pull request #401 from stan-dev/minor-doc-improvements

Clarify doc for `variable` argument to `extract_variable()` and `extract_variable_matrix()`

more diagnostic doc fixes

prepare for release of version 1.5.0

prepare for release of version 1.4.0

minor fixes to references

Merge pull request #180 from stan-dev/remove_stan_repo_install_sugges…

…tion

Cleanup the mention of posterior on stan-dev/r-packages repo

bump version number

fix issue #100

require recent version of rlang, tibble to be safe

old versions of these packages can cause some weird behavior when combined with various versions of other tidyverse/r-lib packages.
@paul-buerkner will add a tag for 0.1.1 because of this

Merge pull request #83 from stan-dev/option-names

standardize and document global option names, closes #82