fix(client): pass correct client reference to root resources

[nestor-diaz]

There is a minor issue that's causing an error executing root resources defined with path params.

Considering this path /{user}, the resulted client is:

class Client {
  ...
  
  user(uriParams) {
    return new User(
      this.client,
      this.path + template('/{user}',
        Object.assign({}, uriParams))
    );
  }
}

Despite user method is defined within Client class, the User class is instantiated with this.client. Such property isn't defined inside Client and in fact, based on the logic, it expects a instance of Client so just providing this fixes the issue.

After applying the fix, that portion of code looks like this:

class Client {
  ...
  
  user(uriParams) {
    return new User(
      this,
      this.path + template('/{user}',
        Object.assign({}, uriParams))
    );
  }
}

[nestor-diaz]

I had to make this change because TSLint failed due to this string concatenation, it expects template literals.

[nestor-diaz]

I had to make this change because TSLint failed due to this string concatenation, it expects template literals.

[nestor-diaz]

I had to make this change because TSLint failed due to it expects two indentation spaces

[nestor-diaz]

Travis CI was failing, after researching a bit I found that dist: trusty is needed if xvfb is used directly.

Doc: https://docs.travis-ci.com/user/gui-and-headless-browsers/#using-xvfb-directly