Generation July 23rd

[SerKnight]

• fix budgets endpoints
  • adds budgetbalance & budgetline
• payments
  • adds bank_amount & reference
• payroll calendar reference date
• PayrollUk Earnings rate EARNINGS_TYPE_TERMINATION_PAY

• ---

• new readme examples for HTTP info
• removed old docs
• downgrades dependency for guzzle psr7 "guzzlehttp/psr7": "^1.8", https://github.com/XeroAPI/xero-php-oauth2/issues/240