Updated README.md
Updated README.md

Added sudo to install instructions. Resolves issue #988
EmpireProject/Empire,adaptivethreat/Empire,byt3bl33d3r/Empire,EmpireProject/Empire,byt3bl33d3r/Empire,EmpireProject/Empire,byt3bl33d3r/Empire,EmpireProject/Empire,PowerShellEmpire/Empire,byt3bl33d3r/Empire,adaptivethreat/Empire,PowerShellEmpire/Empire,adaptivethreat/Empire,byt3bl33d3r/Empire,EmpireProject/Empire,PowerShellEmpire/Empire,EmpireProject/Empire