Travis: Update GCC to GCC 6, 2017q2 release.

.travis.yml

@@ -14,9 +14,9 @@ notifications:
       - "Firmware download : https://portapack-h1-builds.s3.amazonaws.com/%{repository_slug}/%{build_number}/%{build_number}.1/build/firmware/portapack-h1-firmware-%{commit}.tar.bz2"
 
 before_script:
-  - wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/6-2016q4/gcc-arm-none-eabi-6_2-2016q4-20161216-linux.tar.bz2 -O /tmp/gcc-arm.tar.bz2
+  - wget https://developer.arm.com/-/media/Files/downloads/gnu-rm/6-2017q2/gcc-arm-none-eabi-6-2017-q2-update-linux.tar.bz2 -O /tmp/gcc-arm.tar.bz2
   - tar -xf /tmp/gcc-arm.tar.bz2
-  - export PATH=$PWD/gcc-arm-none-eabi-6_2-2016q4/bin:$PATH
+  - export PATH=$PWD/gcc-arm-none-eabi-6-2017-q2-update/bin:$PATH
   - export CC="arm-none-eabi-gcc"
   - export CXX="arm-none-eabi-g++"