v0.4.0 beta release of Open PowerShell

With 255 non-merge commits since v0.3.0, here are the major changes:

- PSReadLine is ported and included by default
- Original Windows ConsoleHost is ported and replaced CoreConsoleHost
- .NET Core packages set to the RC2 release at build 24103
- OS X 10.11 added to Continuous Integration matrix
- Third-party C# cmdlets can be built with .NET CLI
- Improved symlink support on Linux
- Microsoft.Management.Infrastructure.Native replaced with package
- Many more Pester tests
