Fix #536 - Implement linter problem type re-mapping

plugin/ale.vim

@@ -178,6 +178,9 @@ call ale#Set('pattern_options_enabled', !empty(g:ale_pattern_options))
 " A maximum file size for checking for errors.
 call ale#Set('maximum_file_size', 0)
 
+" Remapping of linter problems.
+call ale#Set('type_map', {})
+
 function! ALEInitAuGroups() abort
     " This value used to be a Boolean as a Number, and is now a String.
     let l:text_changed = '' . g:ale_lint_on_text_changed