Please add a license file

[TravisEz13]

Please add a license file so that I can understand if I can use the code or contribute.

Thanks.

[TravisEz13]

The original code is MIT
https://github.com/paulomarquesc/AzureRmStorageTable/blob/master/LICENSE

[rdbartram]

added via #1

[TravisEz13]

@jakedenyer Are you planning on publishing a new version? Do you want me to take ownership of the PowerShell Gallery module?