Update vex-dialog and update docs

[bbatliner]

The yesText/noText options that were proposed in #52 were finally added to vex-dialog.

These features are available with vex-dialog@1.1.0. This issue is tracking what needs to be done to get these in vex proper.

• [x] Update dep in package.json
• [x] Update documentation with new options
• [ ] Publish docs to HubSpot's site
• [x] Bump minor version
• [x] Publish to npm