Removed the redgreen gem, which was messing out the output, and as it
turns out isn't necessary anyway.
Configured the date pickers to auto-close when a value is selected
(should have pushed with redgreen gem change)
Added a Sales section

* Implemented a RevenueCalculator class to encapsulate revenue
  calculations used throughout the system, assuming all models that
  use it have an assotiation to SalesRecord
* Implemented a DatePickerParams class to encapsulate handling the
  from/to date fields used to present the sales calculations