[fix] NOT READY: generator isn't seeded error

When I run the following code, it will lead to `throw new sjcl.exception.notReady (" generator isn't seeded ");` 
So, I patched

```
var ripple  = require('ripple-lib');

config = {
  domain: 'www.rippletrade.com'
}

vaultClient = new ripple.VaultClient(config.domain)


vaultClient.register({
  username: 'kissripple1',
  password: 'password',
  email: 'mproxy@126.com',
  domain: config.domain,
  activateLink: config.domain + '/#/register/activate'
}, function(err, result){
  if (err){
    console.error(err)
  }
  else {
    console.dir(result)
  }
})
```