Instead of UTF-8 with BOM. Resolves #417.
Uses the $IsWindows etc. booleans from the Microsoft.PowerShell.Platform module instead of sourcing Test-Common repeatedly.
- Pester source code moved to `test/Pester`, deleted `ext-src`. - Pester tests (.ps1 files) moved to `test/powershell` - xUnit tests (.cs files) moved to `test/csharp` - Third-party script test moved to `test/shebang`