Exclude nodeValue instanceof RegExp.

```js:fuga.js
(function () {
  var grasp = require('grasp');
  var replacer = grasp.replace('squery', 'literal[val=hoge]', 'fuga');
  console.log(replacer('var a = "hoge";').toString());// var a = fuga;
  console.log(replacer('var a = "hoge";var b = /a/;').toString());// var a = fuga;var b = /a/;
})();
```

```sh
$ node fuga.js 
var a = fuga;

/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:37
    ref$ = syntaxFlat[ast.type], nodes = ref$.nodes, nodeArrays = ref$.nodeArr
                                             ^
TypeError: Cannot read property 'nodes' of undefined
    at visitPre (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:37:46)
    at new Cache (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:10:5)
    at isMatchComplex (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/match.js:495:13)
    at /Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/match.js:131:50
    at visitPre (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:36:5)
    at visitPre (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:46:9)
    at visitPre (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:56:11)
    at visitPre (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/common.js:56:11)
    at matchAst (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/match.js:128:11)
    at matchAst (/Users/monjudoh/temp/grasp/node_modules/grasp/node_modules/grasp-squery/lib/match.js:318:32)
```