Fix exit code for version and help runners

[adam12]

Cast the runner's return value to Integer so we're going to be calling exit with an Integer. The original implementation had a ternary with explicit constants for the two exit codes. I could probably do something similar if the simple cast is insufficient.

Fixes this:

$ standardrb --help
... bunch of help output
TypeError: no implicit conversion from nil to integer
  /workspace/exe/standardrb:7:in `exit'
  /workspace/exe/standardrb:7:in `<top (required)>'
  /usr/local/bundle/bin/standardrb:23:in `load'
  /usr/local/bundle/bin/standardrb:23:in `<top (required)>'

$ standardrb --version
1.0.2
TypeError: no implicit conversion from nil to integer
  /workspace/exe/standardrb:7:in `exit'
  /workspace/exe/standardrb:7:in `<top (required)>'
  /usr/local/bundle/bin/standardrb:23:in `load'
  /usr/local/bundle/bin/standardrb:23:in `<top (required)>'

[searls]

Whoops! That's what I get for blindly trusting @nicksieger!

(jk, Nick's great and I should have thought to try these commands)

[searls]

Landed in 1.0.3!

[nicksieger]

Hey, the tests passed! Sorry about the breakage!