Allow backtick strings to avoid escaping single or double quotes

Fixes standard/standard#421

eslintrc.json

@@ -126,7 +126,7 @@
     "one-var": [2, { "initialized": "never" }],
     "operator-linebreak": [2, "after", { "overrides": { "?": "before", ":": "before" } }],
     "padded-blocks": [2, "never"],
-    "quotes": [2, "single", "avoid-escape"],
+    "quotes": [2, "single", { "avoidEscape": true, "allowTemplateLiterals": true }],
     "rest-spread-spacing": [2, "never"],
     "semi": [2, "never"],
     "semi-spacing": [2, { "before": false, "after": true }],