Added possibility to render Javascript as a response from the server
Refactor out single invoice item to external partial
Use server JS response to render new invoice partial in Invoices#create
Add custom XHR adapter to handle high-level XHR calls
Increment the indicator of total number of invoices when created
Fix request logger breaking in tests
Fix broken controller references in SecuredTest
Add tests for JSON requests to Invoices controller
Add fancy animation when adding an invoice
Add support for using XHR adapter for regular links
Add feature to remove an invoice
Add fancy remove transition
Put increment/decrement invoice counter methods in Util helper object