FeddTag: add func for fetching next feedTag page

[sviande]

Hi this PR : add func Next on feedTag for fetching next pages (Like Hastag.Next)

Usage:

ft, err := inst.Feed.Tags("mytag")
if err != nil {
   return err
}
dosomethingWithItems(ft)
for ft.Next() {
  dosomethingWithItems(ft)
}

return ft.Error()

[ahmdrz]

Are these lines the same as yours?

		newFT := &FeedTag{}
		err = json.Unmarshal(body, newFT)
		if err == nil {
			ft = newFT

[sviande]

Yes it's the same, i copy the code from hashtags.go

[ahmdrz]

Alright, Later I will change both of them.

[ahmdrz]

Thank you @sviande. Can you create some test functions for feed tags? I'll merge it BTW.

[sviande]

Can you create some test functions for feed tags? I'll merge it BTW.

I will add some tests and create a new PR.