Change calculation of Not Budgeted Last Month

Resolves #17

* Not Budgeted Last Month should be last month's Available to Budget. Currently is simply total income minus total budgeted, which doesn't work when there is overspending.

README.md

@@ -20,6 +20,10 @@ Budget Banana is a web-based interface to help you to live out these four rules
 Change Log
 -------------
 
+### v0.1.3 - 2014-10-01 ###
+
+* Fixed calculation of **Not Budgeted Last Month** ([#17](https://github.com/devbanana/Budget-Banana/issues/17))
+
 ### v0.1.2 - 2014-09-18 ###
 
 * Fixed broken images on category page ([#12](https://github.com/devbanana/Budget-Banana/issues/12))

src/Devbanana/BudgetBundle/Entity/BudgetRepository.php

@@ -116,16 +116,17 @@ public function getAvailableToBudget(Budget $budget)
      */
     public function getNotBudgetedLastMonth(Budget $budget)
     {
-        // Get all income assigned to months before this month
-        $totalIncome = $this->getEntityManager()
-            ->getRepository('DevbananaBudgetBundle:LineItem')
-            ->getTotalIncomeBefore($budget);
+        $lastMonth = clone $budget->getMonth();
+        $lastMonth->modify('-1 month');
 
-        $totalBudgeted = $this->getEntityManager()
-            ->getRepository('DevbananaBudgetBundle:BudgetCategories')
-          ->getTotalBudgetedBefore($budget);
+        $lastMonthBudget = $this->findOneByMonth($lastMonth);
 
-            return bcsub($totalIncome, $totalBudgeted, 2);
+        if ($lastMonthBudget) {
+            return $this->getAvailableToBudget($lastMonthBudget);
+        }
+        else {
+            return '0.00';
+        }
     }
 
     public function getOverSpentLastMonth(Budget $budget)