Enable testing via camcorder.

Changes to the core fleecing code to enable automated
testing using the camcorder gem.
Added comcorder based unit tests.

Added camcorder based unit tests for various levels of the fleecing stack.
The intent of these tests is to illustrate usage, so it can be applied to automated tests.
Rubocop clean up.
Added camcorder to lib/Gemfile.
Merge pull request #629 from roliveri/camcorder_tests

Enable fleecing tests via camcorder