Deprecated nom calls

[joshrule]

Noticed these when compiling polytype today:

warning: use of deprecated item 'nom::methods::call_m': Please use the nom-methods crate instead
 --> /Users/rule/sync/josh/library/research/polytype-rs/src/parser.rs:2:16
  |
2 | use nom::{alt, call_m, do_parse, expr_res, map, map_res, method, opt, separated_list, tag, ws};
  |                ^^^^^^
  |
  = note: #[warn(deprecated)] on by default

warning: use of deprecated item 'nom::methods::method': Please use the nom-methods crate instead
 --> /Users/rule/sync/josh/library/research/polytype-rs/src/parser.rs:2:58
  |
2 | use nom::{alt, call_m, do_parse, expr_res, map, map_res, method, opt, separated_list, tag, ws};
  |                                                          ^^^^^^

I don't know if I'll have time to put together the PR for this so wanted to flag it here in case someone else can get to it before I do.

[lorepozo]

I took a closer look at this, seems like nom is in a somewhat inconsistent state right now, in preparation for 5.0. Probably worth restricting the version more tightly (going back to before this warning was occurring) and then upgrade to 5.0 when the time comes.