Merge pull request #8 from tino-junge/rti

Resource Type Inheritance (RTI)
Release 0.23.0 with resource inheritance.
Fix type on ResourceTypeError.
Release 0.23.1
Use hacky delegator also delegating class and instance checks to provide a dynamic class method access.
Release 0.23.2
Use buckler shield instead of own for rubydoc.
Fix typhoeus version.

Due to new mime-types major typhoeus will be auto-resolved to 0.3.3 without version constraint.
Try travis rbx.
Require rubysl on rbx
Add rbx specific gems
Add '1' to allowed boolean TRUE_VALUES
Acfs boolean attribute specs
Merge branch 'master' of github.com:tino-junge/acfs