Handle temporary postgres downtime

- If we lose the postgres connection, try and reconnect
- Cache incoming tweets while waiting for reconnection to PG
- Tweet admin if connection cannot be re-established
- Added tests for factored out tweetAdmin function and new cache mode
behaviour
- This resolves #5
Fixed typo in config variable name 'steamUrl'
Updating JSDoc

- Fixing typo in doc comment
- Rebuilding docs
Stop sending tweets to self

- Enhanced the "don't send to self" code to be configuration driven
- All reply tweets go through the protection
- Updated documentation
- Added tests for send reply tweet behaviour