Removed support for Ruby 1.8.7 from docs
Added basic ON4.0 support
Updated Travis-CI configuration
Support for Ruby 2.0.0 is optional in 0.5.x
Basic contextualization support (based on OCCI-OS)
CONTEXT section is now optional (disabled by def.)
Small fix for CONTEXT section in compute
Updated authN rutines for ON 4+
Added debugging messages
Small fixes

* Debug messages for Basic/Digest
Fixed HTTP Basic Auth
Updated logging behavior
Minor version bump to 0.5.6
Small fix for user_data
Merge pull request #70 from arax/0.5.x

Updates for the legacy branch:
* basic contextualization support
* necessary dependency updates
* basic support for ON 4+
* fixed Basic Auth
* minor logging fixes
* dropped support for Ruby 1.8.7