Fixed selection method to correctly address selections such as Tr[list(integer(0), 2)]. Code cleanups.
Added rgeos as a required dependency to make any over methods for trajectory classes work flawlessly.
Added over method for Track objects. Fixed coercion method.
Added coercion methods to allow for converting trajectories to time series. Code cleanups.
Added coercion methods to allow for converting trajectories to spatio-temporal points.
Added coercion methods to allow for converting trajectories to SpatialPointsDataFrame.
Merge branch 'master' of https://github.com/k2sk8s/spacetime