sperrorest 3.0.0

Breaking

• All parallel modes got removed in favor of using parallelism via package {future}.
  This simplifies usage a lot and helps simplyifing future maintenance.
  Also it gives users the freedom to choose the parallel backend on their own.
• sperrorest() run sequentially by default again rather than in parallel.

Package infrastructure

• Removed the following packages from Imports: {glue}, {purrr}, {doFuture}, {gdata}, {magrittr}, {parallel}, {pbapply}, {pbmcapply}, {foreach}
• Moved the following packages from Imports to Suggests: {rpart}
• Removed the following packages from Suggests: {pacman}, {ipred}, {RSAGA}
• The "spatial-use-case" vignette now runs and is not read-only anymore.