update travis

.travis.yml

@@ -1,30 +1,32 @@
-# Sample .travis.yml for R projects
 
 language: r
-warnings_are_errors: true
-sudo: required
+r:
+  - release
+  - devel
 
-r_packages:
-  - devtools
+sudo: false
+cran: http://cran.at.r-project.org
+
+cache: packages
 
 r_github_packages:
   - jimhester/covr
 
 after_success:
-  - Rscript -e 'library(covr); coveralls()'
-
-env:
- global:
-  - CRAN: http://cran.rstudio.com
-  - NOT_CRAN: true
-  - R_BUILD_ARGS="--resave-data --compact-vignettes=gs+qpdf"
-  - R_CHECK_ARGS="--as-cran --timings"
-  - R_CHECK_TIME="TRUE"
-  - R_CHECK_TESTS="TRUE"
-  - _R_CHECK_TIMINGS_="0"
-  - $BOOTSTRAP_LATEX="TRUE"
+  - Rscript -e 'library(covr);coveralls()'
 
 notifications:
   email:
     on_success: change
-    on_failure: change
+    on_failure: always
+
+env:
+  global:
+    - NOT_CRAN: true
+    - R_BUILD_ARGS="--resave-data --compact-vignettes=gs+qpdf"
+    - R_CHECK_ARGS="--as-cran --timings"
+    - R_CHECK_TIME="TRUE"
+    - R_CHECK_TESTS="TRUE"
+    - _R_CHECK_TIMINGS_="0"
+
+warnings_are_errors: true