Start major refactoring of recurring_todos. Started with creating new recurring todos. 
All current and new tests pass
remove unused code and refactor builder to remove duplication
use new model to handle updating of recurring todos
small cleanups
move mapping of form attributes to model attributes from pattern to builder to make
pattern independent of form
move model validation into pattern classes and link from recurring_todo model
make validations a bit more dry
move form specific accessors out of model
fix updating of recurring todo and create a form helper for filling the recurring todo edit
form
add some more tests
dry form_helper using meta programming.

not sure if this improves readability, but codeclimate should be happier...
add basis tests for patterns and remove doubles from recurring_todo_test.rb
move as_text helpers to respective pattern
move recurrence text helpers into patterns. move next_date calculation into 
respective models
move daily test to daily pattern test
improve test of daily repeat pattern
move tests from recurring_todo_test to respective repeat_pattern_tests
small refactorings and add some tests
smaal refactoring and improvement of date handling in test