EEE::World -> EEE::TestHelper

The old name was motivated by the naming used by Cucumber BDD
framework.  However, out EEE::TestHelper is quite universal.

Ruby version for RVM and rbenv was added.  Also, version was incresed
to reflect bigger changes in API.
Method interface DSL fixed

Interfaces were moved from modules to classes, e.g. ESClient interface
is defined by EEE::Methods::Client class which includes
EEE::Methods::Definition module with DSL.  Definition module was also
refactored to be clearer.

Another change is that require_relative is used instead of old 1.8
idioms.

Everything other change just makes things work.