make df the first argument in get_totals to work more seamlessly with dplyr

[jamesmartherus]

Tidyverse functions generally take the data argument first, making it easier to use the %>% operator. For example:

dec13_excerpt <- dec13_excerpt %>% mutate(fake_weight = coalesce(llweight, cellweight))
get_totals("q1", dec13_excerpt, wt = c("weight", "fake_weight"), include_unw = TRUE)

becomes:

dec13_excerpt <- dec13_excerpt %>%
 mutate(fake_weight = coalesce(llweight, cellweight)) %>%
 get_totals("q1", wt = c("weight", "fake_weight"), include_unw = TRUE)

Happy to submit a PR if you all are interested. This change could be relevant to other functions as well, I haven't checked.

[arnoldlcl]

Thanks for raising this issue! get_totals() was one of the first functions we made and it wasn't designed from the ground up to work with tidyverse and piping. We've been considering making this change in the next release but it would require updating a lot of other bits of code on our end as well, so it's something we need to spec out properly.