Add support to private repositories

[junalmeida]

Instead of asking me my login and password, this module is failing when trying to access a private github repository:

A solicitação foi anulada: Não foi possível criar um canal seguro para SSL/TLS.
No C:\Program Files\WindowsPowerShell\Modules\InstallModuleFromGitHub\1.2\InstallModuleFromGitHub.psm1:40 caractere:19
+                   Invoke-RestMethod $url -OutFile $OutFile
+                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand

[mivalsten]

Hi @junalmeida, I've created pull request #13 that solve both your issues.
The error you pasted is standard powershell error with SSL, you may fix it by running following command first:
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12