AllowAutoRedirect is no longer configurable per request

It was never being set to anything other than true anyway.
Share the http client between requests
Everything is disposable
Reimplement timeout with cancellation tokens
Guard against null CancellationToken
Code formatting
Protected ctor for controlling disposing inner client
Conditional dispose in Connection
Protected disposing conditional constructor in GitHubClient
Be more picky about having an absolute URI
Merge pull request #403 from octokit/niik/reuse-http-client

Pipeline Http requests - for great justice