Query benchpark version

[slabasan]

Version added to argument list:

$ ./bin/benchpark --version
0.1.0

Help menu (now) displays if no arguments provided. This used to be a custom error message: Must specify subcommand: list setup

$ ./bin/benchpark
usage: benchpark [-h] [-V] {list,setup} ...

Benchpark

options:
  -h, --help     show this help message and exit
  -V, --version  show version number and exit

Subcommands:
  {list,setup}
    list         List available benchmarks and systems
    setup        Set up an experiment and prepare it to build/run

$ ./bin/benchpark --help
usage: benchpark [-h] [-V] {list,setup} ...

Benchpark

options:
  -h, --help     show this help message and exit
  -V, --version  show version number and exit

Subcommands:
  {list,setup}
    list         List available benchmarks and systems
    setup        Set up an experiment and prepare it to build/run