0.5.0

New functions

• new function merge_projections permits to join different sets of
  simulations, adapting the respective time windows accordingly

• new function merge_add_projections permits to add simulated case incidence
  from different sets of simulations, adapting the respective time windows
  accordingly; if objects contain different numbers of simulations, the shortest
  ones are recycled as needed; also implemented as the operator +

• new function summary will summarise projections objects by day, using a
  range of pre-defined statistics (mean, sd, min, max, and user-defined
  quantiles)

Fixes and improvements

• bug fix for the use of time-varying R in project

• bug fix for as.data.frame(..., long = TRUE)

• more consistent handling of inputs for the serial interval; if provided as a
  vector, si now starts at a delay of 1 day, rather than 0 and assuming the
  first entry is 0; for distcrete inputs, the mass for si$d(0) is now
  ignored, and the rest of the distribution is rescaled accorindly to ensure the
  PMF sums to 1

• (documentation) more realistic serial interval distribution used for the Ebola
  examples

• (internal) the force of infection is now calculated by the new internal
  function compute_force_infection

• (testing) revised sets of tests relying less on comparison to references,
  but testing for meaningful output properties instead

• (testing) 100% coverage