fix double prefix in devDependencies

package.json

```
{
  "name": "a",
  "devDependencies": {
    "should": "~0.1.0"
  }
}
```

run `autod -f ~` yield

```
[DEPENDENCIES]

  "dependencies": {

  },
  "devDependencies": {
    "should": "~~0.1.0"
  }
```