Documentation corrections

All documentation now compiles with a handful of warnings related to
data members for which we will provide no documentation:

* Splunk.Client.Server.ClassResourceName
* Splunk.Client.Server.Info,
* Splunk.Client.Server.Restart
* Splunk.Client.Server.Settings
* Splunk.Client.ServerMessageCollection.ClassResourceName
Add ConfigureAwait(false) to all async calls. Refactor test suite to use ThrowsAsync. Fixed few tests that were failing.
Replace utility method with raw ConfigureAwait.
Add User-Agent string.
Set version to 2.0 everywhere. Add README and LICENSE to solution.
Add Changelog
Make tests run with SSL3 support enabled.

Add CHANGELOG to solution. Format usings in Context.cs.
Add SSL3 support to examples (besides Windows 8.1 example, which I cannot load on this machine.)
Add SSL3 support to Windows 8.1 app.
Update version in .nuspec files.
Release 2.0