srvyr 1.0.1

survey_mean() with no x no longer errors when there are no grouping variables (#117)

srvyr 1.0.0

summarize has been rearchitected,
- main user facing improvements are:
  - dplyr::across() now works within it
  - dplyr functions like dplyr::cur_group(), dplyr::cur_group_id(), dplyr::cur_data()
    work in it (as well as new anlagous functions srvyr-specific cur_svy() and
    cur_svy_full())
- The only known breaking change is:
  - objects in the summarize will refer to the output of summarize before the input.
    Meaning code that looks like this:
```
dstrata %>% summarize(api99 = survey_mean(api99), api_diff = survey_mean(api00 - api99)) 
```
    will now error because it calculates the mean of api99 before using it inside of the
    calculation for api_diff. This behavior better matches dplyr's so will likely be
    kept.
Support for group_map()/group_walk()/group_map_dfr(), group_split(),
group_nest() and nest_by() were added for tbl_svy objects.
Support drop_na from tidyr (#107).
as_survey() and as_survey_() are now idempotent: given a srvyr survey object (a tbl_srv), they return it unchanged. If extra arguments are provided, they are ignored with a warning (#97, thanks @krivit).
rename_with() now works with surveys (#96, thanks @krivit).