Fixing bad ! conditional in if statement checking for a RegExp or not

With no options passed to express-load the initial options.extlist never gets converted to a RegExp properly due to a bad if conditional.

This PR makes a tiny change to that if so that the default extlist gets converted to a RegExp. I assume this is the intended behavior.

This stack is thrown:

```
{
  "date": "Wed Apr 30 2014 18:31:21 GMT-0700 (PDT)",
  "process": {
    "pid": 16988,
    "uid": 502,
    "gid": 20,
    "cwd": "/Users/_user_/Documents/Work/_project_",
    "execPath": "/usr/local/Cellar/node/0.10.26/bin/node",
    "version": "v0.10.26",
    "argv": [
      "node",
      "/Users/_user_/Documents/Work/_project_/lib/server.js"
    ],
    "memoryUsage": {
      "rss": 29999104,
      "heapTotal": 28055552,
      "heapUsed": 10749448
    }
  },
  "os": {
    "loadavg": [
      2.0615234375,
      1.90234375,
      1.84228515625
    ],
    "uptime": 13155
  },
  "trace": [
    {
      "column": 91,
      "file": "/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js",
      "function": "ExpressLoad.then",
      "line": 107,
      "method": "then",
      "native": false
    },
    {
      "column": 8,
      "file": "/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js",
      "function": "new ExpressLoad",
      "line": 58,
      "method": null,
      "native": false
    },
    {
      "column": 10,
      "file": "/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js",
      "function": "module.exports",
      "line": 287,
      "method": "exports",
      "native": false
    },
    {
      "column": 1,
      "file": "/Users/_user_/Documents/Work/_project_/lib/server.js",
      "function": "",
      "line": 171,
      "method": null,
      "native": false
    },
    {
      "column": 26,
      "file": "module.js",
      "function": "Module._compile",
      "line": 456,
      "method": "_compile",
      "native": false
    },
    {
      "column": 10,
      "file": "module.js",
      "function": "Object.Module._extensions..js",
      "line": 474,
      "method": "Module._extensions..js",
      "native": false
    },
    {
      "column": 32,
      "file": "module.js",
      "function": "Module.load",
      "line": 356,
      "method": "load",
      "native": false
    },
    {
      "column": 12,
      "file": "module.js",
      "function": "Function.Module._load",
      "line": 312,
      "method": "Module._load",
      "native": false
    },
    {
      "column": 10,
      "file": "module.js",
      "function": "Function.Module.runMain",
      "line": 497,
      "method": "Module.runMain",
      "native": false
    },
    {
      "column": 16,
      "file": "node.js",
      "function": "startup",
      "line": 119,
      "method": null,
      "native": false
    }
  ],
  "stack": [
    "TypeError: Object .js,.node,.json,.coffee,.sjs has no method 'test'",
    "    at ExpressLoad.then (/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js:107:91)",
    "    at new ExpressLoad (/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js:58:8)",
    "    at module.exports (/Users/_user_/Documents/Work/_project_/node_modules/express-load/lib/express-load.js:287:10)",
    "    at Object.<anonymous> (/Users/_user_/Documents/Work/_project_/lib/server.js:171:1)",
    "    at Module._compile (module.js:456:26)",
    "    at Object.Module._extensions..js (module.js:474:10)",
    "    at Module.load (module.js:356:32)",
    "    at Function.Module._load (module.js:312:12)",
    "    at Function.Module.runMain (module.js:497:10)",
    "    at startup (node.js:119:16)"
  ],
  "level": "error",
  "message": "uncaughtException: Object .js,.node,.json,.coffee,.sjs has no method 'test'"
}
```