DatePicker ignoring getFirstDayOfWeek in localeUtils (other functions there work as expected)

[kraf]

Bug report

I want to change the first day of the week to Monday via the localeUtils function and it's getting ignored. I tracked this down to a problem in version 2.5.0 in react-day-picker. This seems to be fixed in the new version, I even found a test for this in 3.1.0 which is missing in 2.5.0.

• Package version(s): datetime/1.4.1

Steps to reproduce

1. Create a DatePicker component with a localeUtils object having

getFirstDayOfWeek: () => 1

Actual behavior

First day of week is still Sunday, no matter the return of the function.

Expected behavior

First day of week should be Monday.