Add code validation on submission for Ruby
Mock Language#compiles? for Clojure, Go and Python
Change Language#compiles? to Language#parses?
Include tests for code parsing
Fix Language::Ruby#parses? - shell out
Add Language::Python#parses? method
Refactor spec for parsing Ruby code
Refactor Language::Python#parses?

Check the exit code of py_compile and use it as a result
Stub Language#parses? when testing a submission

This way we test the feature in isolation
Refactor Language::Ruby::parses?

Use exit code to determine if the parsing is successfull. Suppress outputs to avoid test log pollution.
Add Language::Go#parses? method
Refactor specs for Language#parses? method
Add Language::Clojure#parses? method
Add error messages for failed submissions
Reimplement submission with ActiveModel
Add verifications in specs for bad submissions
Split TestRunner module
Replace Language#parse? with Language#parsing?
Sort challenges by created date in ascending order

This is done to match the same order used in tasks.
Fix wrong identation