You could open up a PowerShell instance and run a command like the following:
Get-ChildItem ".\Stored Procedures\*.sql" | ForEach-Object { sqlcmd -S ServerName -d DatabaseName -E -i $_.FullName }
This will get each .sql file in the Stored Procedures directory, and one by one, pass it to the sqlcmd.exe program. To get more details on the parameters for sqlcmd you can run sqlcmd /?.
To make it recursive through sub directories, you can apply the -Recurse parameter to Get-ChildItem along with the -Filter parameter:
Get-ChildItem '.\Stored Procedures' -Filter *.sql -Recurse | ForEach-Object { sqlcmd -S ServerName -d DatabaseName -E -i $_.FullName }