Fix styling of syntax errors

Since we were previously specifying the message type to be `syntax error`, Linter didn't have a pre-defined style for the messages. Move to just using `Error`, which Linter will style for us.

lib/main.js

@@ -51,9 +51,10 @@ export default {
         let match = regex.exec(output);
         while (match !== null) {
           const msgLine = Number.parseInt(match[1] - 1, 10);
+          const type = match[2] === 'warning' ? 'Warning' : 'Error';
           toReturn.push({
             range: helpers.rangeFromLineNumber(textEditor, msgLine),
-            type: match[2],
+            type,
             text: match[3],
             filePath,
           });