Fix `npm install`

[woahdae]

Previously, a fresh install fails due to websocket-driver@0.7.2 being pulled. See:

https://github.com/faye/websocket-driver-node/blob/master/CHANGELOG.md

Lots of issues like ex. https://github.com/faye/websocket-driver-node/issues/34

This bumps websocket-driver to 0.7.3 so npm install succeeds.

What does this PR do? How does it affect users?

Fixes npm install

Related tickets?

Nope

How should this be tested?

Start a fresh project or rm -rf node_modules, then npm install.

Step through the code line by line. Things to keep in mind as you review:

• Are there any edge cases not covered by this code?

N/A

• Does this code follow conventions (naming, formatting, modularization, etc) where applicable?

N/A

Fetch the branch and/or deploy to staging to test the following:

• [✓] Does the code compile without warnings (check shell, console)?
• [✓] Do all tests pass?
• [N/A] Does the UI, pixel by pixel, look exactly as expected (check various screen sizes, including mobile)?
• [N/A] If the feature makes requests from the browser, inspect them in the Web Inspector. Do they look as expected (parameters, headers, etc)?
• [N/A] If the feature sends data to Keen, is the data visible in the project if you run an extraction (include link to collection/query)?
• [N/A] If the feature saves data to a database, can you confirm the data is indeed created in the database?