Don't use index 0 for output

It's easier to read if we start with 1 when outputting what session we just created.
Don't default to 10 sessions created

Instead of always creating 10, let's allow it to be configurable and if no choice is made, let's have it be a random number between 0 and 3 that is created.
Don't make all the same number of sessions for all users by default

passing in the --user_id=X flag allows you to only create sessions for user X

passing in the count=X flag allows us to specify the count of how many sessions we want to create.