Redesigned the library

- Updated the ruby version.
- Use safe yaml from master branch to support ruby 2.2.0-dev
- Updated travis to use latest ruby.
- Support AffiliateOffer http://developers.hasoffers.com/#/affiliate/controller/Affiliate_Offer

Implemented next methods:

* findAll
* findById
* getCategories
* getTargetCountries

- Updated base to use target uri. Use expect style for some tests.
- Extracted make request from Base to sparate class.
- Updated configuration using.