sgo - Simple Geographical Operations (with OSGB36)

• Bumped minimum R required version to 3.5 (sysdata.rda uses workspace format version 3)
• Replaced testthat with tinytest for Unit Testing.
• sgo_coordinates gained a couple of paramaters meant for geodetic coordinates.
• Improved the speed of NGR conversions.
• A little tidy-up of both code and documentation.

sgo - Simple Geographical Operations (with OSGB36)

• Fixed: Now, when converting from 2D BNG to 3D BNG, the input is first converted
  to 3D by filling z with zeros. Previous versions just added zeros to the output.
• Fixed: When converting from 2D to 3D coordinates with the same datum the z
  column was not being filled with zeroes.
• Fixed: Points right on the upper boundaries of the OSTN grid are considered
  outside of the OSTN15 rectangle.
• Fixed: Output text of the print function.
• Improved slightly the speed of 3D calculations from/to BNG.
• Improved some parts of sgo_transforms's documentation.

sgo - Simple Geographical Operations (with OSGB36)

First submission to CRAN