radiatR 0.1.0

• First public release.
• Read and construct movement Tracks, with support for absolute and relative
  coordinate frames and frame-rate / time metadata.
• Plot circular data with radiate(), including axial overlays, faceting,
  grouping, perimeter labelling and circular boxplots.
• Compute kinematics: speed, path sinuosity, per-row velocity angle and related
  trajectory summaries.
• Circular statistics: circular and concentration regression, model selection,
  and tests of mean direction, symmetry and unimodality.
• Interactive Shiny app (inst/app), also deployed at
  https://johnkirwan.shinyapps.io/radiatR/.