request: store an operation reference

To provide middlewares an option to access the operation of the request and
the related information (like which service ...) store the operation inside
the request object.
runner: abort request processing when middleware does not return request

Allow middlewares to abort the request processing as it is needed by
caching middlewares.
Release 0.38 (middleware improvements)
README: correct branch names (as it is now stable-0)
Adjust travis ruby versions
Revert to "rbx"
Merge branch 'stable-0' of git://github.com/jgraichen/acfs into stable-0
Move rbx to allowed failures as it's broken on travis
instrumentation: add acfs.operation.before_process

Add a new instrumentation event which is (in every case) executed before the
operation is finished.
Release 0.39
supplying params for delete to figure out the correct path

* needed for additional parameters, see the specs
Remove useless assignment
Merge pull request #26 from PragTob/fix_destroy_path

Fix destroy path with parameters
Release 0.39.1
Adjust #persisted? logic to be compatible with rails/ActiveModel

* fixes #27 - also see #27 for a more thorough description of
  the differences
Merge pull request #28 from PragTob/fix_persisted

Fix #persisted? to be ActiveModel compliant
Update changelog and version to 0.40.0
Keep rspec at 2.99.x as rspec3 breaks the tests, thanks Travis
Add rubocop config
Add possible thread-safety by using thread-local Acfs.runner