increase swap to fix #37 memory error

This will increase the swap file to 500MB before downloading the lists.
 Most of the issue comes from the mahakala list, which is so large.  If
no swap file is found, one is created.

gravity.sh

@@ -44,6 +44,31 @@ else
 	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
+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
+	}
+	
+if [[ -f /etc/dphys-swapfile ]];then
+	swapSize=$(cat /etc/dphys-swapfile | grep -m1 CONF_SWAPSIZE | cut -d'=' -f2)
+	if [[ $swapSize != 500 ]];then
+		mv /etc/dphys-swapfile /etc/dphys-swapfile.orig
+		echo "** Current swap size is $swapSize"
+		createSwapFile
+	else
+		:
+	fi
+else
+	echo "** No swap file found.  Creating one..."
+	createSwapFile
+fi
+
 # Loop through domain list.  Download each one and remove commented lines (lines beginning with '# 'or '/') and blank lines
 for ((i = 0; i < "${#sources[@]}"; i++))
 do