Update gravity.sh sudo errors as root

When gravity.sh is run as the root user, it errors out on the sudo command.
These changes make the script check to see if it is invoked by the root and sets the sudo variable to handle root and non-root runs.

gravity.sh

@@ -5,6 +5,11 @@
 # This script should only be run after you have a static IP address set on the Pi
 piholeIP=$(hostname -I)
 
+#Checks if the script is being run as root and sets sudo accordingly
+SUDO=''
+if (( $EUID !=0 )); then SUDO='sudo'
+fi
+
 # Ad-list sources--one per line in single quotes
 sources=('https://adaway.org/hosts.txt'
 'http://adblock.gjtech.net/?format=unix-hosts'
@@ -45,7 +50,7 @@ if [[ -d $piholeDir ]];then
 	:
 else
 	echo "** Creating pihole directory..."
-	sudo mkdir $piholeDir
+	$SUDO mkdir $piholeDir
 fi
 
 # Add additional swap to prevent the "Error fork: unable to allocate memory" message:  https://github.com/jacobsalmela/pi-hole/issues/37
@@ -53,10 +58,10 @@ function createSwapFile()
 #########################
 	{
 	echo "** Creating more swap space to accomodate large solar masses..."
-	sudo dphys-swapfile swapoff
-	sudo curl -s -o /etc/dphys-swapfile https://raw.githubusercontent.com/jacobsalmela/pi-hole/master/advanced/dphys-swapfile
-	sudo dphys-swapfile setup
-	sudo dphys-swapfile swapon
+	$SUDO dphys-swapfile swapoff
+	$SUDO curl -s -o /etc/dphys-swapfile https://raw.githubusercontent.com/jacobsalmela/pi-hole/master/advanced/dphys-swapfile
+	$SUDO dphys-swapfile setup
+	$SUDO dphys-swapfile swapon
 	}
 
 
@@ -138,7 +143,7 @@ function gravity_advanced()
 	echo "** Formatting domains into a HOSTS file..."
 	cat $origin/$eventHorizon | awk '{sub(/\r$/,""); print "'"$piholeIP"'" $0}' > $origin/$accretionDisc
 	# Copy the file over as /etc/pihole/gravity.list so dnsmasq can use it
-	sudo cp $origin/$accretionDisc $adList
+	$SUDO cp $origin/$accretionDisc $adList
 	kill -HUP $(pidof dnsmasq)
 	}