README.md: removed `encode a multipass token step` to avoid confusion

[rv15hwakarthik]

The README.md consists of the below code which leads to confusion. The variable token is not used anywhere in the subsequent piece of code.

 // Encode a Multipass token
var token = multipassify.encode(customerData);

[corymsmith]

It's example code of how to use each function so it doesn't need to be used in the subsequent code.