[elm mode] Sync with upstream implementation
[elm mode] Sync with upstream implementation

Modifies this module to reflect changes made to this mode found in https://github.com/elm/elm-lang.org/blob/master/editor/cm/mode/elm.js
codio/CodeMirror,nightwing/CodeMirror,codio/CodeMirror,dperetti/CodeMirror,wingify/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,dperetti/CodeMirror,pabloferz/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,hackmdio/CodeMirror,dperetti/CodeMirror,wingify/CodeMirror,nightwing/CodeMirror,pabloferz/CodeMirror,codio/CodeMirror,pabloferz/CodeMirror