Consider bailing out early when Pinecone variables are unset

[zackproser]

Currently, it's possible to start the app without the two required environment variables being set:

• PINECONE_API_KEY
• PINECONE_ENVIRONMENT

which might be confusing for users, because the app will appear to work but there will be stack trace in the console.

Perhaps we should consider bailing out early, i.e., not starting up successfully if either of these variables are not set.