tiler 0.2.4

tiler 0.2.3

Improved and simplified instructions and expectations for Windows use. Windows users must add OSGeo4W.bat path to system path.
Added leaflet examples of remotely hosted tiles generated by tiler to vignette.
Bug fix related to system path to OSGeo4W.bat being ignored on Windows.

All three gdal2tiles* scripts have been updated to accept a command line argument when called by R that provides a path for any temporary files, i.e., tmp.*.vrt files created by the gdal2tiles* scripts. These were previously accumulating in the system temp folder. The new temporary directory is a sub-directory inside tempdir(). Therefore, it is cleaned up when exiting R. Nevertheless, tile also force deletes this subdirectory immediately after its internal system call to one of the gdal2tiles* scripts returns, so the temporary sub-directory does not even exist for the full duration of the tile call.
Added functions tile_viewer and view_tiles and other supporting functions for generating HTML Leaflet tile preview web page.
Added arguments to tile. tile now generates previewer by default.
Added unit tests.
Updated vignette.

Refactored tile, added arguments including resume and format, changed some argument names.
Added default support for XYZ format tiles in addition to TMS. This brings in another version of gdal2tiles.
Updated documentation.
Added unit tests.

Created tile function for generating map tiles from geographic or non-geographic maps/images.
Created readme with basic example.
Added initial introduction vignette.
Added robust unit tests and other external examples and spot testing of edge cases.