Add simple data stucture to README

README.md

@@ -1,3 +1,20 @@
 # Budgeteer
 
 Budgeting Web-Application
+
+## Data structure
+
+1 User
+N Budgets
+        AccountID[]
+        CategoryID[]
+        PayeeID[]
+
+N Accounts
+        TransactionID[]
+N Categories
+        AssignmentID[]
+N Payees
+
+N Transactions
+N Assignments