Only build site on release branch

.travis.yml

@@ -4,18 +4,19 @@ language: R
 sudo: false
 cache: packages
 
-r:
-- 3.1
-- 3.2
-- oldrel
-- release
-- devel
-
-before_deploy: Rscript -e 'remotes::install_cran("pkgdown")'
-deploy:
-  provider: script
-  script: Rscript -e 'pkgdown::deploy_site_github()'
-  skip_cleanup: true
-
-after_success:
-  - Rscript -e 'covr::codecov()'
+matrix:
+  include:
+  - r: devel
+  - r: release
+    after_success: Rscript -e 'covr::codecov()'
+    before_cache: Rscript -e 'remotes::install_cran("pkgdown")' -e 'remotes::install_github("tidyverse/tidytemplate")'
+    deploy:
+      provider: script
+      script: Rscript -e 'pkgdown::deploy_site_github()'
+      skip_cleanup: true
+      on:
+        condition: $TRAVIS_BRANCH = master || -n $TRAVIS_TAG
+  - r: oldrel
+  - r: 3.3
+  - r: 3.2
+  - r: 3.1