v0.3.0 alpha release of Open PowerShell

Supports Windows, Nano, OS X, Ubuntu 14.04, and CentOS 7.1.

See the Linux installation documentation. Please note that the installation directory has changed from the prior releases.

The Windows version is not an installer, it's simply a folder with a powershell.exe executable.

With 304 non-merge, non-imported commits since v0.2.0, here are the
major changes:

• .NET Core packages are build rc3-24011
• Native Linux commands are not shadowed by aliases
• Get-Help -Online works
• more function respects the Linux $PAGER; defaults to less
• IsWindows, IsLinux, IsOSX, IsCore built-in PowerShell variables added
• Microsoft.PowerShell.Platform removed for the above
• Cross-platform core host is now CoreConsoleHost
• Host now catches exceptions in --command scripts
• Host's shell ID changed to Microsoft.PowerShellCore
• Modules that use C# assemblies can be loaded
• New-Item -ItemType SymbolicLink supports arbitrary targets
• Readline implementation supports multi-line input
• Ctrl-R provides incremental reverse history search
• $Host.UI.RawUI now supported
• Ctrl-K and Ctrl-Y for kill and yank implemented
• Ctrl-L to clear screen now works
• Documentation was completely overhauled
• Many more Pester and xUnit tests added