Use JSON output with vale

Switches all vale instances to JSON output and provides an appropriate
handler for that. Without JSON, no end_col is provided and text
highlighting only catches the first character of every result.

ale_linters/mail/vale.vim

@@ -4,6 +4,6 @@
 call ale#linter#Define('mail', {
 \   'name': 'vale',
 \   'executable': 'vale',
-\   'command': 'vale --output=line %t',
-\   'callback': 'ale#handlers#unix#HandleAsWarning',
+\   'command': 'vale --output=JSON %t',
+\   'callback': 'ale#handlers#vale#Handle',
 \})