Introducing Infinity.Net

Infinity.Net is a C# object model for the Visual Studio Online and
Team Foundation Server REST APIs.  Infinity.Net was extricated from
the Visual Studio Online API library in Summoner, a chat room
notification application <https://github.com/ethomson/summoner>.
Introduce async methods
UserProfile: update API to version 1.0-preview.1
Introduce ProjectClient
Introduce GitClient
TeamRoom: update API to version 1.0-preview.1
client: use an Executor (instead of a base class)

Create a helper executor for clients, instead of them deriving from
a common base class, to prevent base class leakage into the public API.
remove client exception
Introduce documentation on public API functions
Add a README
Introduce changelog, logo
Infinity.Tests: introduce model tests

Introduce tests to ensure that our models are complete, per the
examples visualstudio.com/integrate/reference/reference-vso-overview-vsi
Add Project.GetProject test
Introduce Team model for Project.DefaultTeam
Introduce ProjectCapabilities
SourceControlType -> VersionControlType for consistency
Introduce Project Links
Refactor mock / tests to prepare for updates
Introduce Project.UpdateProject
ModelFixture -> MockClientFixture

ModelFixture was a stupid name.