Feat/graph session scopes

[jobala]

Overview

Updates GraphSession API

The API has changed so that users only has to pass an auth provider. Initially, users had to create options and auth_handler objects.

scopes = ['mail.send', 'user.read']
auth_provider = TokenCredentialAuthProvider(device_credential, scopes)

graph_session = GraphSession(auth_provider)
result = graph_session.get('/me')
print(result.json())

Closes #36

[jobala]

@MIchaelMainer

The following concerns have been addressed

• Optionally set scopes on AuthProvider
• Stopped passing AuthProviderOptions to AuthorizationHandler
• Setting default scopes

[MIchaelMainer]

@jobala I have the remaining concerns:

• Setting user.read as the default scope instead of https://graph.microsoft.com/.default. Why did you make this change?
• Provide in-depth comments to files. Especially document the args, default behaviors, expected exceptions, new/foreign concepts, etc.
• Does this design support incremental consent?

[jobala]

@MIchaelMainer I am working on this PR that builds on top of this. I will add the comments in that branch.