Move Project#create_from_todo to its own class

The point of this is to keep as many things out of the ActiveRecord
objects as possible and use them as just a thin database abstraction
layer.

test/unit/project_from_todo_test.rb

@@ -0,0 +1,22 @@
+require_relative '../test_helper'
+require_relative '../../lib/project_from_todo'
+
+class ProjectFromTodoTest < ActiveSupport::TestCase
+  fixtures :todos
+
+  def test_create_project_from_valid_todo
+    todo = todos(:upgrade_rails)
+    project = ProjectFromTodo.new(todo).create
+    assert_equal project.name, todo.description
+    assert_equal project.description, todo.notes
+    assert_equal project.default_context, todo.context
+  end
+
+  def test_invalid_project_from_invalid_todo
+    todo = todos(:upgrade_rails)
+    todo.description = ""
+    project = ProjectFromTodo.new(todo).create
+    assert_not_nil project
+    assert_equal false, project.valid?
+  end
+end