Build: travis should run on Linux instead of OSX

.travis.yml

@@ -1,12 +1,12 @@
-language: objective-c
-
-env:
-  matrix:
-    - MONO_VERSION="3.10.0"
+language: c
 
 install:
- - wget "http://download.mono-project.com/archive/${MONO_VERSION}/macos-10-x86/MonoFramework-MDK-${MONO_VERSION}.macos10.xamarin.x86.pkg"
- - sudo installer -pkg "MonoFramework-MDK-${MONO_VERSION}.macos10.xamarin.x86.pkg" -target /
+- curl -sLo /tmp/mono.gpg http://download.mono-project.com/repo/xamarin.gpg
+- sudo apt-key add /tmp/mono.gpg
+- sudo sh -c "echo 'deb http://download.mono-project.com/repo/debian wheezy main' >> /etc/apt/sources.list.d/mono-xamarin.list"
+- sudo apt-get update -qq
+- sudo apt-get install -qq mono-complete nuget mono-vbnc fsharp libgdiplus=2.10-3
+- mozroots --import --sync --quiet
 
 script: 
   - ./build.sh Build