ziafazal/api-remove-rounding: remove round in progress

@martynjames  @mattdrayer remove rounding in course avg progress calculation.
May need to cast something to float() here - if completions is an integer and total_completions is an integer, then automatic rounding may take place. e.g. In python ```5/10 = 0```; but ```float(5)/10 = 0.5```