Merge pull request #3119 from hsanson/2269-ktlint-stdin-support

Fix 2269 - use ktlint stdin.

ale_linters/kotlin/ktlint.vim

@@ -6,5 +6,5 @@ call ale#linter#Define('kotlin', {
 \   'executable': 'ktlint',
 \   'command': function('ale#handlers#ktlint#GetCommand'),
 \   'callback': 'ale#handlers#ktlint#Handle',
-\   'lint_file': 1
+\   'output_stream': 'stderr'
 \})