Add host option (#588)

* Added option to configure host

* Updated sample config

src/services/host.js

@@ -0,0 +1,10 @@
+const config = require('./config');
+const env = require('./env');
+
+let environmentHost;
+
+if (process.env.TRILIUM_HOST) {
+    environmentHost = process.env.TRILIUM_HOST;
+}
+
+module.exports = Promise.resolve(environmentHost || config['Network']['host'] || '0.0.0.0');