Endpoint that pushes all unknown transactions into Redis

The intent is to use `electrum notify <address> <app>/electrum_noify?address=&customer_id=`

The app asks electrum for all transactions on that address, and then checks
which ones we *don't* already have recorded in the transactions table.  These
are pushed into Redis to be picked up by a to-be-written job that will write
them to the transactions table after 3 confirmations.

Initial commit