Fix CRAN notes

[eribul]

Possibly mis-spelled words in DESCRIPTION:
  ATC (20:38)
  Charlson (28:55)
  Elixhauser (28:65)
  ICD (19:74)
  RxRisk (29:3)
  arthroplasty (30:29)
  comorbidity (28:27)
  indices (28:39)
  polypharmacy (29:33)

Found the following (possibly) invalid URLs:
  URL: http://doi.org/10.1002/bjs.6930 (moved to https://doi.org/10.1002/bjs.6930)
    From: man/charlson.Rd
    Status: 200
    Message: OK
  URL: http://doi.org/10.1097/MLR.0000000000000326 (moved to https://doi.org/10.1097/MLR.0000000000000326)
    From: man/elixhauser.Rd
    Status: 200
    Message: OK
  URL: http://doi.org/10.1097/MLR.0000000000000735 (moved to https://doi.org/10.1097/MLR.0000000000000735)
    From: man/elixhauser.Rd
    Status: 200
    Message: OK
  URL: https://docs.ropensci.org/coder (moved to https://docs.ropensci.org/coder/)
    From: DESCRIPTION
          man/coder-package.Rd
    Status: 200
    Message: OK
  URL: https://joss.theoj.org/papers/49d52b062aa289d7b990b1a0a678d109 (moved to https://joss.theoj.org/papers/10.21105/joss.02916)
    From: README.md
    Status: 200
    Message: OK
  URL: https://ropensci.github.io/coder/
    From: inst/doc/coder.html
    Status: 404
    Message: Not Found

Found the following URLs which should use \doi (with the DOI name only):
  File 'charlson.Rd':
    http://doi.org/10.1002/bjs.6930
    https://doi.org/10.1016/0895-4356(92)90133-8
  File 'elixhauser.Rd':
    http://doi.org/10.1097/MLR.0000000000000735
    http://doi.org/10.1097/MLR.0000000000000326
  File 'rxriskv.Rd':
    https://doi.org/10.1016/j.diabres.2009.10.019
    https://doi.org/10.1136/bmjopen-2017-021122

[eribul]

* checking top-level files ... NOTE
Non-standard file/directory found at top level:
  'references.bib'

[eribul]

* checking R code for possible problems ... [7s] NOTE
categorize.codified: no visible binding for global variable
  '...data_cols'
codify.data.table: no visible binding for global variable '..code'
Undefined global functions or variables:
  ...data_cols ..code