v1.0.0

Breaking changes:

• Dropped support for Ruby 1.9.3 from v1.0.0
• Replaced Barge backend with official DigitalOcean's DropletKit.
• Extracted shared specs for better external integration testing.

Changes:

• Fixed specs for DropletKit.
• Added example of custom adapter.
• Added pre-liminal ruby 2.4 support (master branch, travis).