Use 4.8 series GCC compiler for Travis build tests

Since 4.9 is known to create broken CC3D and Sparky builds

.travis.yml

@@ -17,8 +17,16 @@ env:
 # We use cpp for unit tests, and c for the main project.
 language: cpp
 compiler: clang
-before_install: sudo add-apt-repository -y ppa:terry.guo/gcc-arm-embedded && sudo apt-get update
-install: sudo apt-get install build-essential gcc-arm-none-eabi git
+
+before_install: 
+  - sudo apt-get update
+  # The PPA doesn't have a package for Trusty for 4.8, so manually download the Saucy build
+  - wget "http://ppa.launchpad.net/terry.guo/gcc-arm-embedded/ubuntu/pool/main/g/gcc-arm-none-eabi/gcc-arm-none-eabi_4-8-2014q2-0saucy9_amd64.deb"
+
+install: 
+   - sudo apt-get install build-essential git
+   - sudo dpkg -i gcc-arm-none-eabi_4-8-2014q2-0saucy9_amd64.deb
+   
 before_script: arm-none-eabi-gcc --version
 script: ./.travis.sh