Improve gemspec dependencies and requires

Using latest Bundler convencions tought `bundle gem my_gem`
Drop old structure, in order to get cleaner setup
Add basic test structure powered by RSpec
Add README

TODO:

- Add contributing guide
- Basic gem usage
Find Movie by id, introducing Movie API wrapper
Handle attributes wrapping in the Movie class
Add usage instruction into README
Use attr_reader instead accessor, attributes are read only
Resolve endpoint automatically, based on class name
Cut down a feel lines with ternary operator on a simple conditional
Add modular Search feature
Handle search return like activerecord when gathering from a resource

It means that calling TmdbEasy::Search.fetch will return ordinary
results as Hashes, while calling TmdbEasy::Movie will return movie
objects
Extract common behavior from endpoints classes