Server host binding

[inertia186]

As a testnet maintainer, I would like the tinman server module to bind the host on 0.0.0.0, so that external browsers can access the module.

In development, I was always testing http://localhost:5000/account_create, but when deploying to a docker container, it couldn't be accessed, even with -p 5000:5000. Turns out, Flask defaults host bindings to 127.0.0.1.

After merging this pull request, the following script will launch the tinman server module to host the account creation form (/account_create) on port 5000, assuming that the same host is serving the steemd API on port 8091:

#!/bin/bash

cd $HOME

source ~/ve/tinman/bin/activate

jq ".shared_secret=\"$SHARED_SECRET\"" $HOME/tinman/server.conf.example > $HOME/server.conf.temp
jq ".transaction_target.node=\"http://127.0.0.1:8091\"" $HOME/server.conf.temp > $HOME/server.conf
rm $HOME/server.conf.temp

echo tintoy: starting server on port 5000
tinman server \
  --get-dev-key $UTILS/get_dev_key \
  --signer $UTILS/sign_transaction \
  --timeout 600 \
  --chain-id $CHAIN_ID