Added some 2.0.0 build environments
:mock -> :double
Method call mocking changed in spec/lib/thumbnailer_spec.rb
Fixed gems source
Changed default rspec formatter to 'progress'
Moved all settings from .rspec to spec_helper
Merge branch 'feature/fix-specs-deprecations' into develop
Added develop branch to the tests
Readme addition
Version bump and Changelog addition
Merge branch 'release/0.1.3'

This release includes some documentation, versioning and tests improvements.