key_properties node missing from discovery call

[jbaldwin01-sfhp]

Hi guys,

I tried running this package and ran into an error where the key_properties node was missing from the catalog.json file that is generated using the discover method. When I put "key_properties": "id" into each of the JSON for each of the streams in the catalog.json file, I solved the problem. The key_properties node needs to be re-exported into the catalog file when the code is run.

[devanshmalik]

Hey!

I've created a PR #32 to resolve this issue and would appreciate a review! :)