Cubist

* Maintenance release to fix CRAN issues for GCC 10 -fno-common flag.

* `tidy_rules()` was removed since the code is now in the tidyrules package.

* Changes to better work with tibble inputs.

* Maintenance release to fix CRAN issues for C string buffers

* Fixed a bug in the code that escapes improper characters.

* Converted documentation to `roxygen2`.

* Revised some compiler options to reduce `R CMD check` warnings.

* A bug was fixed, found by Duncan Murdoch.
* A bug in predictions when sampling was used was fixed by Laurae (a random data witch/magician) \issue{1}

* Memory allocation bugs in the R version of the C code, which lead to segmentation faults, were fixed.