Crash if uniform_bin MaxSize is not greater than MinSize

[engelsanchez]

If you try to run with {value_generator, {uniform_bin, 5000000, 5000000}}.

The following happens:

13:46:56.762 [debug] Driver basho_bench_driver_riakc_pb crashed: {function_clause,[{random,uniform,[0],[{file,"random.erl"},{line,111}]},{basho_bench_valgen,'-new/2-fun-5-',3,[{file,"src/basho_bench_valgen.erl"},{line,47}]},{basho_bench_driver_riakc_pb,run,4,[{file,"src/basho_bench_driver_riakc_pb.erl"},{line,170}]},{basho_bench_worker,worker_next_op2,2,[{file,"src/basho_bench_worker.erl"},{line,233}]},{basho_bench_worker,worker_next_op,1,[{file,"src/basho_bench_worker.erl"},{line,239}]},{basho_bench_worker,rate_worker_run_loop,2,[{file,"src/basho_bench_worker.erl"},{line,330}]}]}
13:46:56.762 [error] Worker <0.111.0> exited with crash

Suggest validating it before execution and warning end user

[engelsanchez]

@aggress I made some simple changes to improve in the situation for some generators that can be easily validated. I tried to do as much as I could without going into any major architectural changes, as general validation of functional values would take some time to get right. With this, these validators with simple numeric parameters will fail early with an "invalid generator" message pointing out the invalid value (though without a long explanation as to why it was incorrect).

[slfritchie]

Sorry this sat unattended for so long. +1, thanks!