Gem simplification

* Add a few Ruby version manager files to .gitignore. Remove Gemfile.lock.
* Use random test running for RSpec. Remove extraneous puts.
* Use secure RubyGems URL
* Update copyright year in LICENSE
* Add version file
* Cleanup authy.gemspec
* Simplify Rakefile
* Use double instead of mock as mock is deprecated in newer RSpec
Adjust copyright in README as well
Update copyright notices.
Fix httpclient dependency.

The generated gem wasn't installed because it had a wrong version.