Fix #22 - manage systems before setSystemIndex

spec/tiny_spec.lua

@@ -310,4 +310,14 @@ describe('tiny-ecs:', function()
         assert.are.same(_G, GLOBALS)
     end)
 
+    it("Can set system indices", function()
+        local world = tiny.world()
+        local systemA = tiny.system()
+        local systemB = tiny.system()
+        world:addSystem(systemA)
+        world:addSystem(systemB)
+        world:setSystemIndex(systemA, 1)
+        assert(true)
+    end)
+
 end)

test.lua

@@ -0,0 +1,8 @@
+local tiny = require('tiny')
+
+local world = tiny.world()
+local systemA = tiny.system()
+local systemB = tiny.system()
+world:addSystem(systemA)
+world:addSystem(systemB)
+world:setSystemIndex(systemA, 1)

tiny.lua

@@ -821,6 +821,7 @@ end
 -- the order in which they Systems processed, because lower indexed Systems are
 -- processed first. Returns the old system.index.
 function tiny.setSystemIndex(world, system, index)
+    tiny_manageSystems(world)
     local oldIndex = system.index
     local systems = world.systems