Make it possible to add custom validators to node via acts_as_node
Improve Releaf::ContentController#resource_params: don't allow user to
update content_type
Call .name for class instead of .to_s to set node#content_type
Validate length of strings
Remove unused Releaf::Node#content_string
Extend Releaf::Node#data column max size
Add/update varisous model validations
use rails-settings-cached 0.3.1
use string instread of class for class_name
Refactor common fields code
Update dummy app and fix seeds
Get rid of unused constant Releaf::Node::COMMON_FIELDS_SCHEMA
Fix issue with deleting Releaf::Node, when content object can't be constantized

If calss that was referenced by Releaf::Node was deleted from project.
Destroying such node would be impossible, because NameError exception
would be raised by rails (trying to destroy related object),

In case this exception is raised we set content_id and content_type to
nil to eliminate polymorphic association and save node without
validating it (otherwise rails somehow tries to destroy related object.
ie ignores unsaved changed).
After record is saved we call destroy again.
Cleanup node content relation definition
Prepend DummyNode to dummy classes in node spec
require pry and pry-nav gems in spec_helper

This helps debuggig, so you don't have to manually require these gems in
your tests
Use save! to raise errors if validations fail, when saving record
Write test for Releaf::Node#content_class
Optimize query
use foo.present? instead of !foo.blank?