Mongo reconnect

[tomsaleeba]

Steps:

1. start Paratoo using the uwsgi method described in the readme
2. do a GET to trigger the connection to Mongo
3. stop the mongodb
4. do another GET, these should fail
5. start mongodb again
6. do a final GET

Expected behaviour:
Paratoo should attempt to reconnect the mongodb.

Actual behaviour:
The GET request hangs and ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused is eventually returned after 30 seconds.

More details:
Using the issue-6 branch.