Rewrite shell script OS detection to please Travis.

build/InstallMono.sh

@@ -1,24 +1,10 @@
-osis()
-{
-    local n=0
-    if [[ "$1" = "-n" ]]; then n=1;shift; fi
-
-    # echo $OS|grep $1 -i >/dev/null
-    uname -s |grep -i "$1" >/dev/null
-
-    return $(( $n ^ $? ))
-}
-
-osis Darwin &&
-{
+OS=$(uname -s)
+if [ "$OS" == "Darwin" ]; then
 	wget -O mono.pkg http://download.mono-project.com/archive/4.2.1/macos-10-x86/MonoFramework-MDK-4.2.1.102.macos10.xamarin.x86.pkg
 	sudo installer -pkg mono.pkg -target /
-}
-
-osis Linux &&
-{
+elif [ "$OS" == "Linux" ]; then
 	sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
 	echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list
 	sudo apt-get update -qq
 	sudo apt-get install -y mono-devel
-}
+fi