Merge pull request react-bootstrap#1203 from AlexKVal/no-undef

Fix for airbnb bug about 'no-undef' rule.

Author: taion

.eslintrc

@@ -34,6 +34,7 @@
     "no-this-before-super": 2,
     "no-throw-literal": 0,
     "no-underscore-dangle": 0,
+    "no-undef": 2,
     "no-unused-vars": [2, { "vars": "all", "args": "none" }],
     "no-use-before-define": 0,
     "no-var": 2,