Small typo in documentation substract method

I have searched the issues of this repo and believe that this is not a duplicate.

Issue

There is a small typo in the doc for the pendulum object's subtract method.

>>> dt = dt.subtract(minutes=1)
'2012-01-28 01:01:00'
>>> dt = dt.subtract(minutes=24)
'2012-01-28 00:00:00'

The result of dt.subtract(minutes=24) is wrong, it should be 2012-01-28 00:37:00

Can I work on this?

docs: fix incorrect example outputs in addition_subtraction.md

I've opened a PR to fix this: #949

Three incorrect values were found:

add(hours=1) result showed '2012-02-25' instead of '2012-01-29'
subtract(hours=1) result showed '2012-02-29' instead of '2012-01-29' (also impossible date in context)
subtract(minutes=24) from 01:01:00 showed '00:00:00' instead of '00:37:00'