Discard results if editor’s contents have been modified

Fixes #200. See also https://github.com/AtomLinter/linter-eslint/blob/v8.2.1/src/main.js#L187-L195.

lib/linter-js-standard.js

@@ -69,6 +69,13 @@ module.exports = function (textEditor) {
 
   return Q.allSettled(lintPromises)
     .then(function (results) {
+      if (textEditor.getText() !== fileContent) {
+        // When the editor’s contents have been modified since we’ve started
+        // linting, we can’t be sure that the results are still valid.
+        // Therefore, we simply return `null` as not to update the results.
+        return null
+      }
+
       var occurrences = []
 
       results.forEach(function (result) {