replace-vars doesn't handle vars inside JavaScript literal. i.e {foo: '${bar}'}

```
main> (h/sniptest "<script> var require = {baseUrl : '${cdn-js}'}; </script>" #{[:script h/any-node]}(h/replace-vars {:cdn-js "foo"}))
NullPointerException   java.util.regex.Matcher.quoteReplacement (Matcher.java:598)
main> (h/sniptest "<script> var require = baseUrl : '${cdn-js}'; </script>" #{[:script h/any-node]} (h/replace-vars {:cdn-js "foo"}))
"<script> var require = baseUrl : 'foo'; </script>"
```

This doesn't work:
```
  <script>
      var  require = {
      baseUrl : "${cdn-js}"
      };
    </script>
```

Workaround:
```
  <script>
      var  base = "${cdn-js}",
            require = {
                baseUrl : base
            };
    </script>
```