Make the client get method private.

Only need to expose the endpoint helper methods. The
get method should be private.

- Remove code comments for get method.
Handle dependencies in the gemspec.

- Move dependencies into nikeplusgem.gemspec file.
- Include reference to gemspec in Gemfile.
Update gemspec to follow better practices.

- Load files in gemspec via $LOAD_PATH.
- Require the nikeplusgem/version file.
- Remove the setting of the date property.
- Include the test files.
- Set the platform to Ruby.
- Set require_paths to array instead of appending.