Create a mechanism to invoke toys without rubygems for better performance

[dazuma]

Toys can now be run in a Ruby VM that does not have Rubygems loaded up-front. So there's the potential of about 50ms faster startup if we can disable Rubygems. However, Toys is currently installed as a gem, and the Rubygems provides the frontend for its executable.

Create a mechanism to invoke Toys in a Ruby that has Rubygems disabled. This would be particularly useful for the shell completion scripts, which are sensitive to startup time.

Some initial ideas:

• Rewrite the completion script to bypass the Rubygems executable and invoke Ruby directly with --disable=gems. There are some complications here, notably if the user installs a new version of Toys, or changes the current Ruby using a tool such as rbenv, the completion script might end up pointing at an old Toys installation.
• Provide a system command that installs an alternate bin "pinning" to the current Toys installation (although this may exhibit the same complications).
• Experiment with using a non-Ruby script as the executable. Not sure what Rubygems will do with such an executable, though.