Changes in version 0.1.7
* Fixed a C warning.

Changes in version 0.1.6
* deal with a deprecated `<<` operator for `arma` objects in version 11.2.3.

Changes in version 0.1.5
 * better usage of single instruction, multiple data (SIMD) when compiling with
   e.g. -O3 -mtune=native.

Changes in version 0.1.0 to 0.1.4
 * first submission to CRAN.
 * bug fixes of bugs found on CRAN's checks.
