Strict ISO 8601 parser

[ParthGandhi]

There are times when you want to enforce a standard format. Any interest in adding a parse_iso8601 to the library? Can simply delegate to iso8601 or have a new implementation if you don't want to import another lib.

I can send out a PR if you're OK with this.

[myusuf3]

@ParthGandhi hey thanks for the message! I am ok with this please respect current api and flow of application. I would love to see this with some docs and corresponding tests! I will work with you to get this in for sure.