Ability to customize the header

[maxdow]

It could be nice if we can customize how the header show and format the dates.

For example my use case :
I want to have the headerLabel showing current week ( like week 31 ) or current month and subHeaderLabel only display the day

[mariusandra]

Hi, it would be nice. Unfortunately I don't have the resources (time) to do this. Feel free to submit a PR if you get the chance yourself.