Shiny app spit and polish

This is minor release that includes small bug-fixes in package functions and in the built-in shiny app.

• In the SCD_effect_sizes Shiny app:
  • Corrected a bug in the single-series calculator that caused an error when showing the graphed data.
  • Added a message in the single-series calculator to clarify minimum number of data points.
  • In the multiple-series calculator, redesigned the plotting interface the available choices for each filtering variable are calculated after applying the previous filters.