Merge branch 'fix/config' into 'master'

follow node-config submodule pattern

See merge request !9

src/index.js

+process.env.SUPPRESS_NO_CONFIG_WARNING = true
+
 const config = require('config')
 const validations = require('./validations')
 const { get } = require('lodash/fp')
 
 const loggerFromConfig = get('pubsweet-server.logger', config)
 
+config.util.setModuleDefaults('pubsweet-server.logger', loggerFromConfig)
+
 let logger = validations.validateConfig(loggerFromConfig)
 let configured = Boolean(logger)
 

test/index.test.js

 'use strict'
 
 process.env.ALLOW_CONFIG_MUTATIONS = true
-process.env.SUPPRESS_NO_CONFIG_WARNING = true
 
 let config = require('config')
 config['pubsweet-server'] = { }