Because our Smart-TV had only LAN built in I wanted to use the RPi 3 to bridge WiFi to LAN.
This tutorial worked for me before I updated to a later raspbian version:
I adapted it a bit until it worked for me on raspbian stretch 2017-07-09
The configuration file of the DHCP Client (dhcpcd5) /etc/dhcpcd.conf is used instead of /etc/network/interfaces.
Upgrade everything. Install rpi-update and dnsmasq. Run rpi-update => reboot.
Connect to WiFi
Add your network credentials
Static DHCPCD Configuration
Add this OR uncomment the example and modify
Backup dnsmasq.conf and create new
Add configuration for DNS & DHCP-Server (dnsmasq)
Enable IPv4 forwarding
Uncomment this line