- Added cost functions: Llobera-Sluckin’s metabolic energy expenditure; Alberti’s Tobler hiking function modified for animal foraging excursions.

- unlike v0.1, the cost calculation is not based on a slope raster (in degrees) derived from the input dtm; instead, the procedure described in van Etten, “R Package gdistance: Distances and Routes on Geographical Grids” in Journal of Statistical Software 76(13), 2017, pp. 14-15 is followed. The altitudinal difference between dtm cells is first calculated and then divided by cell centres distance, so obtaining slope values (expressed as rise over run) changing according to the direction of movement. This has the important implication that the implemented cost functions are now truly anisotropic;
- color ramp of the output accumulated cost raster has been changed.

first release to CRAN.