Update Invoice creation parameters

• Merge pull request #108 from mychaelgo/master c6caf80
• feat(invoice): add parameter items & fees f61ca60
• Merge branch 'invoice/customer-object' a382897
• test(va): fix amount to satisfy min 10k condition 111688e
• feat(invoice): add customer object when create invoice 0a0ab6e
• fix(invoice): update payer_email & description to optional 732121a

v1.15.0...v1.16.0