Note when SecureRandom#uuid was introduced.

Explain dependency on uuidtools: uuid-serve was created before
SecureRandom#uuid was widely available from the Ruby Standard Library.
Specify Ruby 2.1.1 in Gemfile.
Use up-to-date gem source.
Remove external dependency on uuidtools.
Use updated bundle.
Use SecureRandom instead of UUIDTools.

Generate UUIDs from the standard library instead of from an external
gem.
Update copyright notices.
Update description of purpose.

Update the explanation for the tool's existence, and why one might still
choose to use it.
Merge branch 'feature/secure_random' into master.

Modernize uuid-serve and explain legacy purpose. Specifically:

  - Update gem source.
  - Specify Ruby 2.1.1 in Gemfile.
  - Update bundle.
  - Use SecureRandom from the standard library instead of an external
    dependency on UUIDTools.
  - Update description of purpose and explain the tool's historical
    necessity.
  - Update copyright notices.