Moved void from SalesReceipt service to Invoice service

Merge pull request #6 from renedekat/void-invoice

Move void to Invoice

v0.1.17

Added void method

v0.1.16

Changes

Added helper methods to SalesReceipt builder

v0.1.15

Changes

Fixed delete method

v0.1.14

Changes

Added setters in Invoice item builder

v0.1.13

Changes

Added setId method to QBClass builder.

v0.1.12

Changes

Added setName method to QBClass builder

v0.1.11

Restored static variable

v0.1.10

Changes

Added setters in Customer, Builder and Address builders

v0.1.9

Fixes

PSR namespace