upgrades RedCloth dependency to ~> 4.2, adds RedCloth to the project's Rakefile, removes gem call from the guides generator (use bundle exec if needed)

Reuse the view_context from the controller, this make the test environment more similar to the code applications uses

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

In AS, only inflector/methods is need in proxy_wrappers.rb, as well as date, date_time, and time conversions.rb. This fixes an issue when requiring json and AS saying that i18n is also required.
Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

test_with_polymorphic_and_condition works without the conditions methods in BelongsToPolymorphicAssociation because the conditions are added straight to the association_scope as of a few days ago

Refactor the code for singular association constructors. This will allow me to define a create_association! method in a minute.

Get rid of set_association_target and association_loaded? as the parts of the code that need that can now just use association_proxy(:name).loaded?/target=