Invoke-WebRequest and Invoke-RestMethod are slow because of the progress bar

[mpiederiet]

Some of the dependency scripts (in particular PSDependScripts\Github.ps1) use Invoke-WebRequest and Invoke-Restmethod to download files. As described on multiple sites, this is very slow because of the shown progress bar: PowerShell/PowerShell#2238.

Proposed solution:
(PSDepend\Github.ps1, Line 448, replace with following lines):
$PreviousProgressPreference=$ProgressPreference
$ProgressPreference='SilentlyContinue'
Invoke-RestMethod -Uri $URL -OutFile $OutFile
$ProgressPreference=$PreviousProgressPreference