Bento v0.0.8

• Introduce an improvement to banks: a Bank class
  • handles boilerplate
  • will allow more version control and support banks as plugins
  • easier to work with when managing a collection of banks
• Add a bit more to the beginner tutorial, fix a few typos, update to match new bank syntax
• Add the date_control bank which can ultimately supercede the prior date_slider, range_slider, date_pickers all-in-one