Sign ps1xml

Fixes pester#1356

signModule.ps1

@@ -2,7 +2,7 @@ param($Thumbprint)
 $ErrorActionPreference = 'Stop'
 
 $cert = Get-ChildItem Cert:\CurrentUser\My |
-    where Thumbprint -eq $Thumbprint
+Where-Object Thumbprint -eq $Thumbprint
 
 if ($null -eq $cert) {
     throw "No certificate was found."
@@ -14,8 +14,8 @@ if (@($cert).Length -gt 1) {
 
 "Signing Files"
 $files = Get-ChildItem -Recurse -ErrorAction SilentlyContinue |
-    Where-Object { $_.Extension -in ".ps1", ".psm1", ".psd1", ".dll" } |
-    Select-Object -ExpandProperty FullName
+Where-Object { $_.Extension -in ".ps1", ".psm1", ".psd1", ".ps1xml", ".dll" } |
+Select-Object -ExpandProperty FullName
 
 $incorrectSignatures = Get-AuthenticodeSignature -FilePath $files | Where-Object { "Valid", "NotSigned" -notcontains $_.Status }
 if ($incorrectSignatures) {
@@ -29,7 +29,7 @@ if (-not @($filesToSign)) {
 }
 
 $results = $filesToSign |
-    ForEach-Object {
+ForEach-Object {
     $r = Set-AuthenticodeSignature $_ -Certificate $cert -TimestampServer 'http://timestamp.digicert.com' -ErrorAction Stop
     $r | Out-String | Write-Host
     $r