Add Travis CI config to build Marlin firmware.

.travis.yml

+---
+language: c
+
+before_install:
+  - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+  - sudo apt-get update -qq
+install:
+  - sudo apt-get install -qq gcc-avr binutils-avr avr-libc gcc-4.8 g++-4.8 arduino
+  - sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 90
+  - sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 90
+  - gcc --version
+  - g++ --version
+
+script: "cd Marlin && make HARDWARE_MOTHERBOARD=70 ARDUINO_INSTALL_DIR=/usr/share/arduino"

README.md

@@ -2,6 +2,7 @@
 Marlin 3D Printer Firmware
 ==========================
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/2224/badge.svg)](https://scan.coverity.com/projects/2224)
+[![Travis Build Status](https://travis-ci.org/ErikZalm/Marlin.svg)](https://travis-ci.org/ErikZalm/Marlin)
 
 Marlin has a GPL license because I believe in open development.
 Please do not use this code in products (3D printers, CNC etc) that are closed source or are crippled by a patent.