Adding challenge window size selections

[tilley-kyle]

We are adding in the capability for a merchant to select what size they would like their instance of RJS to display the 3ds challenge iframe.

To test. Supply the challengeWindowSize field in the call to 3DS Risk. Your site should be set on sandbox and you can use a sandbox 3ds card to trigger a transaction.
Example:

risk.ThreeDSecure({
  actionTokenId: myActionTokenId,
  challengeWindowSize: risk.ThreeDSecure.CHALLENGE_WINDOW_SIZE_01_250_X_400,
});

or

risk.ThreeDSecure({
  actionTokenId: myActionTokenId,
  challengeWindowSize: '01',
});

[coveralls]

Coverage increased (+0.04%) to 92.636% when pulling 53c5b22 on 3ds-window-sizing into e4233b4 on master.

[douglaslise]

Just a small suggestion, feel free to ignore if not apply.
In general it's a good job 👏

Requirements changed

[chrissrogers]

Awesome PR!