leverage custom writer in vdiffr

.travis.yml

@@ -3,17 +3,10 @@ cache: packages
 sudo: true
 dist: trusty
 warnings_are_errors: false
-
-matrix:
-  include:
-    - r:
-      - devel
-      - oldrel
-      - release
-        # run visual tests
-        # TODO: push the svg files somewhere on after_failure?
-        before_script: docker run -e MAPBOX_TOKEN=$MAPBOX_TOKEN -v $(pwd):/home/plotly --privileged cpsievert/plotly-orca R -e "devtools::install_deps('/home/plotly', dep = T); res <- devtools::test('/home/plotly', reporter='summary'); df <- as.data.frame(res); if (sum(df\$failed) > 0 || any(df\$error)) q(status=1)"
-
+r:
+  - devel
+  - oldrel
+  - release
 
 env:
   global:
@@ -33,5 +26,8 @@ before_install:
   # make sure R pkgs are upt-to-date
   - Rscript -e 'update.packages(ask = FALSE)'
 
+before_script:
+  - if [[ "$TRAVIS_R_VERSION_STRING" == "release" ]]; then docker run -e MAPBOX_TOKEN=$MAPBOX_TOKEN -e VMODE="ci" -v $(pwd):/home/plotly --privileged cpsievert/plotly-orca; fi
+
 # work around temporary travis + R 3.5 bug
 r_packages: devtools  

inst/docker/Dockerfile.vtest

@@ -86,7 +86,7 @@ RUN printf '#!/bin/bash \nxvfb-run --auto-servernum --server-args "-screen 0 640
 RUN chmod 777 /usr/bin/orca
 
 # install visual testing packages
-RUN R -e "devtools::install_github('cpsievert/vdiffr@diffObj')"
+RUN R -e "devtools::install_github('lionel-/vdiffr')"
 RUN R -e "devtools::install_github('brodieG/diffobj@development')"
 
 # switch on visual testing