make non-bare-name args start with "."

[mjskay]

Nevermind, point_interval turned out to be the only sensible function for this so far. [gather|spread]_[predicted|fitted]_samples I will deal with when I get there (see #63).

Decide if I want to do this on functions that don't have naming conflicts. Not going to do this on stats/geoms (to maintain consistency with ggplot naming scheme).

• add_predicted_samples(newdata, model, var = "pred", ..., n = NULL), add_fitted_samples, predicted_samples, fitted_samples
  • Doing it here would make names consistent with [spread|gather]_[fitted|predicted]_samples once those functions are made. Although gather/spread are going to need another arg (like ".args") to hold the args for predicted/fitted_samples due to already using ... to take the models, so this isn't actually needed.
• compare_levels(samples, variable, by, fun=-, comparison = default, indices = c(".chain", ".iteration"))
  • Only would have wanted it if we ever add renaming capability, which we probably don't need, and/or could do as another argument.
• [spread|gather]_samples(model, ..., regex = FALSE)
  • Again, probably not. Renaming is easy enough after extraction if desired, and hard to fit into the DSL here.
• gather_terms(data, ignore_columns = "^\..*")
  • No reason it would. If the output column names change that will be as arguments giving new names as strings