Feature/implement generic add

[Anshuman71]

Implement the add(Object) function from Moment and fix #1427

Add 2 hours, 15 minutes and 30 seconds to 10 July 2014 12:45:00;

var result = add(new Date(2014, 6, 10, 12, 45, 0), { minutes: 15, hours: 2, seconds: 30 });
result: Thu Jul 10 2014 15:00:30

Supports adding

{
hours: number,
years: number,
days: number,
quarters: number,
weeks: number,
months: number,
minutes: number,
seconds: number,
milliseconds: number
}
combined in a single call

[kossnocorp]

@Anshuman71 thank you a lot!

[Anshuman71]

@Anshuman71 thank you a lot!

Can you please help me with this failing test?

[kossnocorp]

@Anshuman71 sure, I'm working on a review atm, and tests will pass once you address my comments. Please stay put.

[kossnocorp]

Great and very important work, thank you so much! Please address my comments before we proceed. I didn't check the date math yet, I will do with the second review round.

[kossnocorp]

@Anshuman71 I'm going to push some changes in the PR. I reevaluated how other functions handle incorrect arguments, and now I think RangeError is a wrong approach. I also want to adjust tests a bit. Please don't push anything.

[Anshuman71]

@Anshuman71 I'm going to push some changes in the PR. I reevaluated how other functions handle incorrect arguments, and now I think RangeError is a wrong approach. I also want to adjust tests a bit. Please don't push anything.

Sure, go ahead

[kossnocorp]

I've pushed some changes. Most notable changes are:

• I've rolled back the Invalid Error on invalid duration. You were right returning it.
• I've removed weeks and milliseconds to make the duration object correspond to ISO 8601's duration. This will help us down the road when we are going to add support to it the library.
• I reused addMonths to avoid copy-paste of the code with quirks.

[kossnocorp]

Great work!

[Anshuman71]

Great work!

@kossnocorp thanks for your help in shipping the feature

[kossnocorp]

You're welcome!