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.

lib/project_from_todo.rb

@@ -0,0 +1,27 @@
+class ProjectFromTodo
+  attr_reader :todo
+
+  def initialize(todo)
+    @todo = todo
+  end
+
+  def create
+    project = build_project
+
+    if project.valid?
+      todo.destroy
+      project.save!
+    end
+
+    project
+  end
+
+  def build_project
+    project = Project.new.tap do |p|
+      p.name = todo.description
+      p.description = todo.notes
+      p.default_context = todo.context
+      p.user = todo.user
+    end
+  end
+end