Added junit test cases for BudgetCategoryImpl.
Output: Test result was all passed.
 Extracted Methods: public long getAmount(Date startDate, Date endDate) is extracted into 2 new methods named sameStartEndBudgetPeriod() and overlapStartEndBudgetPeriod()
Introduced 3 Explaining Variables to public long getAmount() to simply the complexity of the conditional expression.
Merge remote-tracking branch 'origin/Conditional_Complexity-CodeSmell'