Bump minimum Clojure version to 1.5.0

Let's stay current.
Add an intermediary TestRunner::Results class

The main goal is to remove the TestRunner class and replace it
with code in Language.run_test
Rebrand test_runner spec as a Ruby runner
Rename failures_count to failed_count
Decouple spec from TestRunner
Remove the TestRunner class
Redo the Python runner to be consistent with Ruby
Add a clojure test runner
Oops. Remove a debug leftover
Clojure test runner doesn't choke on unnamed tests
Make rake task:dump:solutions work for all langs
Add timeout to the clojure runner
Don't show solution log if task is not closed
Add the sidekiq role to capistrano
Add a checked column to ChallengeSolution
Add more photo sizes

The new sizes are: 150x150, 80x80, 50x50 and 30x30. Not all are used,
but probably all would be useful.

Another important change is that all of them are now named consistently,
thus no need to select the user in order to predict the filename of
their photo. This is a breaking change and it requires regenerating all
versions. This can be done with:

    rake users:photos:recreate

This should be executed after the code is deployed.
Improve the challenge interface a bit
Make the challenge test case editable
Extract checking queued jobs to a module
Generalize QueueMonitoring to work with any task