Prettify install script (#248)

@zaquestion

install.sh

@@ -1,27 +1,43 @@
 #!/usr/bin/env bash
 
 set -e
-[[ -z $DEBUG ]] || set -x
 
-if [ $EUID != 0 ]; then
+if [[ ! -z $DEBUG ]]; then
+    set -x
+fi
+
+if [[ $EUID != 0 ]]; then
     sudo "$0" "$@"
-    exit $?
+    exit "$?"
 fi
 
-machine=""
-case $(uname -m) in
-x86_64) machine="amd64";;
-i386) machine="386";;
+case "$(uname -m)" in
+    x86_64)
+        machine="amd64"
+        ;;
+    i386)
+        machine="386"
+        ;;
+    *)
+        machine=""
+        ;;
 esac
 
-os=""
 case $(uname -s) in
-Linux)  os="linux";;
-Darwin) os="darwin";;
-*)      echo "OS not supported" && exit 1;;
+    Linux)
+        os="linux"
+        ;;
+    Darwin)
+        os="darwin"
+        ;;
+    *)
+        echo "OS not supported"
+        exit 1
+        ;;
 esac
 
-latest=$(curl -sL 'https://api.github.com/repos/zaquestion/lab/releases/latest' | grep tag_name | grep --only 'v[0-9\.]\+' | cut -c2-)
+latest="$(curl -sL 'https://api.github.com/repos/zaquestion/lab/releases/latest' | grep 'tag_name' | grep --only 'v[0-9\.]\+' | cut -c 2-)"
+
 curl -sL "https://github.com/zaquestion/lab/releases/download/v${latest}/lab_${latest}_${os}_${machine}.tar.gz" | tar -C /tmp/ -xzf -
 cp /tmp/lab /usr/local/bin/lab
 echo "Successfully installed lab into /usr/local/bin/"