-S does not check for valid range (0,1)

[teuben]

A simple mistake of using '-S 1234' ran into a coredump. I should have used '-s 1234' instead I was giving an out of range value to the mass segregation -S flag. This resulted in some illegal value in a function, causing an integer used as index to be negative, causing th coredump.

There could be other parameters that were not checked for validity.

[cmaureir]

I opened a pull request that will solve that issue #11