Added modules.lua and check fuel

The app now checks, if it has enough fuel, before doing any movement.

Tree_Farm/choptree.lua

@@ -1,5 +1,6 @@
 --[[Tree Chopping program by Sascha
 Chops down the tree in front of turtle.]]
+os.loadAPI('modules.lua') -- Load the modules module
 
 print('Chopping tree...')
 
@@ -7,15 +8,17 @@ if not turtle.dig() then -- chop base of tree
   error('Turtle needs a digging tool!')
 end
 
-os.sleep(5) -- Wait until everything droppen from the tree
+os.sleep(3) -- Wait until everything droppen from the tree
 for j = 1, 4 do
-    for i = 1, 4 do
-        turtle.suck() -- Suck up everything
-	turtle.turnLeft()
-    end
-    turtle.forward()
+  for i = 1, 4 do
+    turtle.suck() -- Suck up everything
+    turtle.turnLeft()
+  end
+  check_fuel()
+  turtle.forward()
 end
 
 for i = 1, 4 do
-    turtle.back()
+  check_fuel()
+  turtle.back()
 end