Rename package and project

[scarrazza]

Given that we are planning to support multiple providers, I think we should rename this package in qibo-providers and just mention the names of the providers in the documentation (at the moment TIIProvider).

[scarrazza]

@marcorossi5, I have already changed the github name.

[scarrazza]

@marcorossi5, thinking more about this, could you please perform the following changes:

• rename this project as qibo-client
• create an abstract Client class, which should takes the web service url and token.
• rename the TIIProvider class in a def TII(token): function which should return the allocated Client(tii_url, token)

I believe this change is good because we are planning to have another family of cloud backends directly integrated in Qibo's set/get backend mechanism, therefore this client can be integrated easily with that system, and furthermore it is not really needed to create special providers for different labs using a similar approach to TII.

[marcorossi5]

Yes, it seems clean. I'll code this in a couple of days.