Utilize async/await

Use the much cleaner async/await syntax to clean up the code around the
execution of `ruby`.

Author: Arcanemagus

lib/main.js

@@ -15,7 +15,7 @@ export default {
       grammarScopes: ['source.ruby', 'source.ruby.rails', 'source.ruby.rspec'],
       scope: 'file',
       lintOnFly: true,
-      lint: (activeEditor) => {
+      lint: async (activeEditor) => {
         const command = atom.config.get('linter-ruby.rubyExecutablePath');
         const ignored = atom.config.get('linter-ruby.ignoredExtensions');
         const filePath = activeEditor.getPath();
@@ -25,23 +25,27 @@ export default {
           return [];
         }
 
-        return helpers.exec(command, ['-wc', '-E utf-8'], { stdin: activeEditor.getText(), stream: 'stderr' }).then((output) => {
-          const toReturn = [];
-          output.split(/\r?\n/).forEach((line) => {
-            const matches = regex.exec(line);
-            if (matches === null) {
-              return;
-            }
-            const msgLine = Number.parseInt(matches[1] - 1, 10);
-            toReturn.push({
-              range: helpers.rangeFromLineNumber(activeEditor, msgLine),
-              type: matches[2],
-              text: matches[3],
-              filePath,
-            });
+        const execArgs = ['-wc', '-E utf-8'];
+        const execOpts = {
+          stdin: activeEditor.getText(),
+          stream: 'stderr',
+        };
+        const output = await helpers.exec(command, execArgs, execOpts);
+        const toReturn = [];
+        output.split(/\r?\n/).forEach((line) => {
+          const matches = regex.exec(line);
+          if (matches === null) {
+            return;
+          }
+          const msgLine = Number.parseInt(matches[1] - 1, 10);
+          toReturn.push({
+            range: helpers.rangeFromLineNumber(activeEditor, msgLine),
+            type: matches[2],
+            text: matches[3],
+            filePath,
           });
-          return toReturn;
         });
+        return toReturn;
       },
     };
   },