Update syntax checking

* Line continuation characters should be on the same lines.
* .vim file line indentation should be a multiple of 4.

ale_linters/markdown/markdownlint.vim

@@ -2,10 +2,10 @@
 " Description: Adds support for markdownlint
 
 call ale#linter#Define('markdown', {
-    \ 'name': 'markdownlint',
-    \ 'executable': 'markdownlint',
-    \ 'lint_file': 1,
-    \ 'output_stream': 'both',
-    \ 'command': 'markdownlint %s',
-    \ 'callback': 'ale#handlers#markdownlint#Handle'
-\ })
+\   'name': 'markdownlint',
+\   'executable': 'markdownlint',
+\   'lint_file': 1,
+\   'output_stream': 'both',
+\   'command': 'markdownlint %s',
+\   'callback': 'ale#handlers#markdownlint#Handle'
+\})