Fix inability to get weeks from Timespan.Humanize

[AKTheKnight]

This fixes an issue I saw on SO below:
https://stackoverflow.com/questions/56550059/humanizer-months-weeks-days-hours

Basically you can't seem to get a value like "3 Months, 2 Weeks, 3 Days, 4 Hours" from calling the below:
new TimeSpan(109, 4, 0, 0, 0).Humanize(3, maxUnit: TimeUnit.Month)

This fixes that (and tests that therefore broke) by changing how we calculate Weeks and Days.

Also fixes #862

[SimonCropp]

@MihaMarkic @hangy @hazzik any thoughts on this one. i have no objections

[MihaMarkic]

@SimonCropp It's a tough one. I see the use for both, but one without weeks might be better because it's shorter and we are more used to it in general. Said that, I'd opt for an option to display one or another as I guess people have different use cases and opinions.

[clairernovotny]

Just need to ensure the CLA is signed and conflicts resolved

[AKTheKnight]

I've fixed the conflicts, however unsurprisingly this breaks two tests from different cultures that aren't expecting to suddenly be provided weeks.

Not sure if it would be preferable to make the returning of weeks optional as suggested above, or to make it a breaking change and remove the broken tests/find people who can help fix the test to now get weeks in return