Add GPL license, better readme and flash-tool

Setting it up so it's a propper project which can be released. It's
still not showing any temperature and there is no description of
how to set up the hardware yet.

README.md

@@ -2,7 +2,38 @@
 
 This is my first stab at a wireless termometer.
 
+## Getting the code
+
+    git clone https://github.com/jeena/esp8266-temperature.git
+    cd esp8266-temperature
+    git submodule init
+    git submodule update
+
+## Setup
+
 It expects a credentials.lua file with content like this:
 
     SSID = "myssid"
-    PASSWORD = "mypasswd"
+    PASSWORD = "mypasswd"
+
+Copy the credentials.lua.example file into credentials.lua and change
+it so et matches your wifi credentials.
+
+## Flashing
+
+To put the code onto the ESP8266 you need the luatool which is
+included as a git submodule.
+
+Use flash.sh to flash it via /dev/ttyUSB0
+
+## License
+
+This file is part of esp8266-temperature.
+
+Copyright 2017 Jeena
+
+esp8266-temperature is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+
+esp8266-temperature is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with esp8266-temperature. If not, see http://www.gnu.org/licenses/.