Add Gifs, Update Stars and Videos

[SashaSZ]

Added:
Gifs with methods getGifs and getGif, that similar like Videos methods. Sorting parameters: sort_by and period

Updated:

1. Stars:
   a) Added getStar method, that give more detail information. Also added full_data argument to getStars
   b) Added sorting parameters: period and p_type
2. Videos: Added sorting parameters: period and region
3. Client: Added the ability to specify sorting when initializing the client, example:

# Daily most viewed video in Argentina
client = pornhub.PornHub(sort_by="view", period="day", region="ar")
for video in client.getVideos(10, page=2):
    print(video["views"])

[sskender]

Does this fix issues #20 and #22 ?

[sskender]

This is a new feature, so in the future please use feat/<feat_name> branch for this kind of PRs.

[sskender]

Can you replace using hard coded integers for sorting with enums? It would be a much more elegant way for this kind of job.

https://docs.python.org/3/library/enum.html

[sskender]

This should not be all in one PR. Please, in the future, use feat/<feature_name> branch name for new features and fix/<issue> branch name for fixing bugs. Also, commit messages like Update ... do not tell much about what was changed and for what purpose.

I will merge it after all comments are resolved for now.