Add support for OAuth Web Flow

This adds support for developers who want to implement the OAuth web flow
with GitHub authentication. https://developer.github.com/v3/oauth/
enable SIMPLE_JSON_READONLY_COLLECTIONS for release configurations
Merge pull request #461 from octokit/release-mode-get-on-board

enable SIMPLE_JSON_READONLY_COLLECTIONS for release configurations
Implement OAuth Web Flow

Provide methods to make it easy for developers to implement the
web flow.

https://developer.github.com/v3/oauth/#web-application-flow
We don't need to make this property public after all
Do not lower case user supplied value

That value might legit need upper and lower case such as the state in an
oauth call.
Implement observable oauth client

Rx will never die
Implemented Get / IsMember for teams

Issue #331.
Added integration tests and a new attribute that requires a new environment variable with an organization to test.

Conflicts:
	Octokit.Tests.Integration/Octokit.Tests.Integration.csproj
Update documentation on how to run the integration tests.
Fix build errors from renamed ITeamsClient members.
Added VS settings file that contains the current project coding conventions.

It can be automatically applied by the QuickSettings extension, or done manually by the developer.
Merge pull request #465 from kzu/AddVsSettings

Added VS settings file that contains the current project coding conventions
Added missing reactive members.
Fixed code analysis issue with naming of Get
Added missing check for empty/null login and its tests
Fix up the mono projects
Merge pull request #449 from kzu/GetAndIsMember

Implemented Get / IsMember for teams
Added GetMembers to retrieve all team members.
Fixed indenting.

Conflicts:
	Octokit.Tests/Clients/TeamsClientTests.cs
Added tests for the observable teams client.