Command Line Runner accepts negative int arguments

[Vladimir Sitnikov]

Just for the reference, error messages are like

$ java -jar benchmarks.jar -help -i -146
Error parsing command line:
 Cannot parse argument '-146' of option ['i']. The given value -146
should be positive

$ java -jar benchmarks.jar -help -wi -42
Error parsing command line:
 Cannot parse argument '-42' of option ['wi']. The given value -42
should be greater or equal than 0


"Forks" argument is optional, thus joptsimple just assumes -1 is the
next option.

$ java -jar benchmarks.jar -help -f -1
Error parsing command line:
 '1' is not a recognized option

Vladimir