Fix external requests on LDP::Resource

Avoid LDP requests for etags, etc... on non-existing resources. Fix
Resource#delete (which was not fully implemented.

Test `OriginalRecord#==`.
Update travis config to use new containers
Merge pull request #38 from dpla/travis-container

Update travis config to use new containers
Add queueing of activities, starting with harvests

This changeset adds a general queueing mechanism and a specific
implementation of harvest queueing, using Resque.

The tests in spec/models and the comment in Krikri::SoftwareAgent
describe how harvest jobs are put onto the queue and run.

- add Resque, with its dependence on Redis
- Create Krikri::Job, which is extended by particular types of jobs.
- Add Resque console, mounted on top of Krikri's path, on ./resque.
- Update Activity model
- Add queueing-related methods to SoftwareAgent
- Add Timecop dependency for testing.
Merge pull request #35 from dpla/feature/queueing

Add initial queueing mechanism
Merge pull request #37 from dpla/feature/ldp-fixes

Fix external requests on LDP::Resource
Add tagged logging to SoftwareAgent
Change scope of logger in SoftwareAgent

Turn @@logger into module constant Logger.

Besides making Rubocop happy, this expresses more what I'd originally
meant:  that all SoftwareAgents should share one logger.
Update rubocop to ignore Vagrantfile and Guardfile
Merge pull request #42 from dpla/rubocop-update

Update rubocop to ignore Vagrantfile and Guardfile
Merge pull request #41 from dpla/feature/tagged-logging

Add tagged logging to SoftwareAgent
Move files from app/models to lib

- Move classes and modules that are not model-like (that don't do
  persistence) into lib.
- Update autoloading in the engine's bootstrapping as a result of this
- Clean up some autoload statements in krikri.rb as a result of the
  autoloading changes.
Merge pull request #43 from dpla/rearrange-modules

Move files from app/models to lib
Update Marmotta to the final 3.3.0 release
Merge pull request #44 from dpla/marmotta-3.3.0

Update Marmotta to the final 3.3.0 release
Add JSON record factory
JSONParser implementation
Merge pull request #40 from dpla/feature/json-parser

JSON parser
[WIP] first hack at a working enrichment
[WIP] add enrichment autoloads