Add Custom Fields

[hbcondo]

Please add CRUD support for Custom Fields. See PR #91 for additional info. Thank you.

[ThomasPe]

I'd gladly accept a PR that includes tests & documentation :)

[TheGameVlog]

I'd gladly accept a PR that includes tests & documentation :)

Ahh so tests & documentation have not been added yet.. is there an alternate method to push Custom Fields data when calling CreatePost as of now?

[Larocceau]

I'm also interested in this feature!