Install dev version of devtools

.travis.yml

@@ -24,7 +24,7 @@ install:
   - bundle install --jobs=3 --retry=3
   - mkdir -p "$R_LIBS_USER"
   - Rscript -e 'if (length(find.package("devtools", quiet = TRUE)) == 0L) { install.packages("devtools", repos = "http://cran.rstudio.com") }'
-  - Rscript -e 'devtools::update_packages("devtools", repos = "http://cran.rstudio.com")'
+  - Rscript -e 'devtools::install_gitihub("hadley/devtools")'
   - Rscript -e 'devtools::install_deps(repos = "http://cran.rstudio.com", dependencies = TRUE)'
 
 script: bundle exec jekyll build