requests parameters not available in SDKs or cache keys

[jamesls]

Consider this route:

@app.route('/users/{user}')
def users(): pass

When we create the method request, we're not actually specifying the "user" value as a requestParameter.

The API will still work as expected, however, there's a few features that can't be leveraged unless we specify them including:

• The generated javascript SDK won't include the "user" as a parameter. Instead it will render a path for /users.
• The "user" parameter isn't available as part of the cache key when caching is enabled.

Neither of these matter yet for chalice because these features aren't exposed, but I'd like to add support for these so I'll need to get this updated.