The `Get-Process` cmdlet cannot be used for these types of tests due to
security constraints on OS X.
These tests are about to be re-written soon anyway, so the simple fix
was to use another cmdlet.
- 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`
