gnu: r-lattice: Update to 0.20-34.

* gnu/packages/statistics.scm (r-lattice): Update to 0.20-34.

gnu: r-plotrix: Update to 3.6-3.

* gnu/packages/statistics.scm (r-plotrix): Update to 3.6-3.

gnu: r-readr: Update to 1.0.0.

* gnu/packages/statistics.scm (r-readr): Update to 1.0.0.
[propagated-inputs]: Add "r-hms", "r-tibble", and "r-r6".

gnu: Add r-hms.

* gnu/packages/statistics.scm (r-hms): New variable.

gnu: Add r-tibble.

* gnu/packages/statistics.scm (r-tibble): New variable.

gnu: r-withr: Update to 1.0.2.

* gnu/packages/statistics.scm (r-withr): Update to 1.0.2.

gnu: r-devtools: Update to 1.12.0.

* gnu/packages/statistics.scm (r-devtools): Update to 1.12.0.

gnu: r-rstudioapi: Update to 0.6.

* gnu/packages/statistics.scm (r-rstudioapi): Update to 0.6.

gnu: r-httr: Update to 1.2.1.

* gnu/packages/statistics.scm (r-httr): Update to 1.2.1.

gnu: r-openssl: Update to 0.9.4.

* gnu/packages/statistics.scm (r-openssl): Update to 0.9.4.

gnu: r-rversions: Update to 1.0.3.

* gnu/packages/statistics.scm (r-rversions): Update to 1.0.3.

gnu: r-multitaper: Update to 1.0-12.

* gnu/packages/statistics.scm (r-multitaper): Update to 1.0-12.

gnu: r-xml2: Update to 1.0.0.

* gnu/packages/statistics.scm (r-xml2): Update to 1.0.0.

gnu: r-r6: Update to 2.1.3.

* gnu/packages/statistics.scm (r-r6): Update to 2.1.3.

gnu: r-crayon: Update to 1.3.2.

* gnu/packages/statistics.scm (r-crayon): Update to 1.3.2.

gnu: r-knitr: Update to 1.14.

* gnu/packages/statistics.scm (r-knitr): Update to 1.14.

gnu: r-mime: Update to 0.5.

* gnu/packages/statistics.scm (r-mime): Update to 0.5.

gnu: r-dbi: Update to 0.5-1.

* gnu/packages/statistics.scm (r-dbi): Update to 0.5-1.

gnu: r-lazyeval: Update to 0.2.0.

* gnu/packages/statistics.scm (r-lazyeval): Update to 0.2.0.

gnu: r-stringr: Update to 1.1.0.

* gnu/packages/statistics.scm (r-stringr): Update to 1.1.0.