write ruby, jruby, rbx mock test helper exes

[Jon]

• respond to --version with full description. Extract description string into external JSON file so that a single exe can be easily configured to provided multiple description strings, e.g. - 1.8.7, 1.9.3, 2.0.0, 2.1.0
• respond to invocation with any number of args by printing to stdout something like [MOCK] executing ${exe} with ${args.join(' ')} and return success code
• can go test be hijacked so mock exes are built to run on same platform as part of test setup? Or should it all be abstracted into the rake test target?

[Jon]

No real need at this time for this.