Could not working `FROM` fields then fixed.

[uribo]

Currently, both CRAN and GitHub versions had Dockerfile$new()'s FROM option were unable to change.

``` r install.packages("dockerfiler") #> #> The downloaded binary packages are in #> /var/folders/0x/mb63hycs4k30_7httqyxh2rr0000gn/T//RtmplVlPBc/downloaded_packages library(dockerfiler) my_dock <- Dockerfile$new(FROM = "rocker/tidyverse") my_dock #> FROM rocker/r-base ``` ``` r remotes::install_github("ColinFay/dockerfiler") #> Using github PAT from envvar GITHUB_PAT #> Downloading GitHub repo ColinFay/dockerfiler@master #> Skipping 1 packages ahead of CRAN: rlang library(dockerfiler) my_dock <- Dockerfile$new(FROM = "rocker/tidyverse") my_dock #> FROM rocker/r-base ``` Created on 2018-03-13 by the [reprex package](http://reprex.tidyverse.org) (v0.2.0).

This patch will allow to specify any dokcer image.

``` r library(dockerfiler) my_dock <- Dockerfile$new(FROM = "rocker/tidyverse") my_dock #> FROM rocker/tidyverse ``` Created on 2018-03-13 by the [reprex package](http://reprex.tidyverse.org) (v0.2.0).

p.s. Thanks for nice package development. I’m fanboy R and Docker too 🐳

[ColinFay]

Thanks @uribo for the patch !